HostAggregateMetadata can't be removed

[zhongkuiGuo]

• First, I add a metadata (cpu_allocation_ratio) to hostAggregate and success !

• Then, I want to delete this metadata , set this metadata value to null and send request :

Executing Request: POST http://novahost:8774/v2.1/os-aggregates/11/action, Headers -> {X-Auth-Token=gAAAAABgk1n......, User-Agent=OpenStack4j / OpenStack Client}, Params -> null, Body -> HostAggregateMetadata{metadata={cpu_allocation_ratio=null}}, Json -> null:50

• It returned success ,but don't remove this metadata.

• I watch the nova host , don't receive the request body :
  {
  "set_metadata" : {
  "metadata" : { }
  }
  }

[zhongkuiGuo]

@olivergondza @drerik @frsyuki @gondor HELP!