Fix for NFS3 primary storage pool is failing to come out of maintenan… (#71)

Fix for NFS3 primary storage pool is failing to come out of maintenance
mode

### Description

This PR has the following:

1. For NetworkFileSystem type, libvirtd handles mounting and unmounting
of nfs mount [Ref: https://libvirt.org/storage.html]
2. KVM adaptor hasn't overridden `deleteStoragePool` method leading to
only just the change in the DB. This was leading to error in case of
`Cancel Maintenance` as the pool already exists with the host.
3. Also, when `Enable Maintenance` call comes, it was first removing the
nfs mount, which was causing the libvirtd to error out during `Destroy
Pool` call as the mount wasn't available.

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### Types of changes

- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] New feature (non-breaking change which adds functionality)
- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] Enhancement (improves an existing feature and functionality)
- [ ] Cleanup (Code refactoring and cleanup, that may add test cases)
- [ ] Build/CI
- [ ] Test (unit or integration test code)

### Feature/Enhancement Scale or Bug Severity

#### Feature/Enhancement Scale

- [] Major
- [ ] Minor

#### Bug Severity

- [ ] BLOCKER
- [ ] Critical
- [X] Major
- [ ] Minor
- [ ] Trivial

### Screenshots (if appropriate):

### How Has This Been Tested?

`Previously:`

<img width="1035" height="362" alt="Screenshot 2026-07-08 at 8 00 05 AM"
src="https://github.com/user-attachments/assets/91a3bcd7-cb6f-4b53-81f5-0851abd337ee"
/>
<img width="1301" height="365" alt="Screenshot 2026-07-08 at 7 58 31 AM"
src="https://github.com/user-attachments/assets/5444b1ae-5cfa-4709-a48f-107b8a257e29"
/>
<img width="1035" height="362" alt="Screenshot 2026-07-08 at 8 00 29 AM"
src="https://github.com/user-attachments/assets/bbeaece1-8795-46ef-b1c7-9a9b24910b21"
/>
<img width="1301" height="327" alt="Screenshot 2026-07-08 at 8 01 37 AM"
src="https://github.com/user-attachments/assets/c9086ef2-066c-4661-a684-c4788e471fdc"
/>

So, clearly though the nfs mount was removed, the libvirtd still has the
pool details with it.

`Now:`

<img width="1042" height="351" alt="Screenshot 2026-07-08 at 8 30 46 AM"
src="https://github.com/user-attachments/assets/59d2c629-41bd-4991-9988-3989dd3497aa"
/>
<img width="1300" height="382" alt="Screenshot 2026-07-08 at 8 31 18 AM"
src="https://github.com/user-attachments/assets/9b774243-8329-4fb8-babb-a0891d20fc6a"
/>
<img width="1043" height="355" alt="Screenshot 2026-07-08 at 8 32 41 AM"
src="https://github.com/user-attachments/assets/5207517a-c2d0-4935-adf0-db70877b79fa"
/>
<img width="1299" height="312" alt="Screenshot 2026-07-08 at 8 33 02 AM"
src="https://github.com/user-attachments/assets/fd5014bb-8d46-423b-8039-b2caa391b885"
/>
<img width="1049" height="340" alt="Screenshot 2026-07-08 at 8 34 32 AM"
src="https://github.com/user-attachments/assets/ec951783-a90e-4118-89d2-8d62b28f138e"
/>
<img width="1299" height="365" alt="Screenshot 2026-07-08 at 8 33 46 AM"
src="https://github.com/user-attachments/assets/a64a2c86-9089-4f67-a345-90a0dbfa88fc"
/>

Author: sandeeplocharla

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/storage/KVMStoragePoolManager.java

@@ -417,7 +417,7 @@ public boolean deleteStoragePool(StoragePoolType type, String uuid) {
         if (type == StoragePoolType.NetworkFilesystem) {
             _haMonitor.removeStoragePool(uuid);
         }
-        boolean deleteStatus = adaptor.deleteStoragePool(uuid);;
+        boolean deleteStatus = adaptor.deleteStoragePool(uuid);
         synchronized (_storagePools) {
             _storagePools.remove(uuid);
         }
@@ -426,10 +426,12 @@ public boolean deleteStoragePool(StoragePoolType type, String uuid) {
 
     public boolean deleteStoragePool(StoragePoolType type, String uuid, Map<String, String> details) {
         StorageAdaptor adaptor = getStorageAdaptor(type);
+        // For NetworkFilesystem, libvirt will take care of unmounting the nfs mount. If nfs mount has been removed before libvirt's pool
+        // delete, libvirt will throw an error.
+        boolean deleteStatus = adaptor.deleteStoragePool(uuid, details);
         if (type == StoragePoolType.NetworkFilesystem) {
             _haMonitor.removeStoragePool(uuid);
         }
-        boolean deleteStatus = adaptor.deleteStoragePool(uuid, details);
         synchronized (_storagePools) {
             _storagePools.remove(uuid);
         }

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/storage/LibvirtStorageAdaptor.java

@@ -905,6 +905,11 @@ private boolean destroyStoragePoolHandleException(Connect conn, String uuid)
         return false;
     }
 
+    @Override
+    public boolean deleteStoragePool(String uuid, Map<String, String> details) {
+        return deleteStoragePool(uuid);
+    }
+
     @Override
     public boolean deleteStoragePool(String uuid) {
         logger.info("Attempting to remove storage pool " + uuid + " from libvirt");