After commit 8f3ac4a switched daos_eq_poll from DAOS_EQ_WAIT to
DAOS_EQ_NOWAIT, two bugs were introduced in kv_put and kv_get:

1. Stale evp dereference on poll failure: when the inner spin loop
   exits with rc < 0 (poll error), evp is NOT updated by daos_eq_poll.
   The code then falls through to access evp->ev_error and call
   daos_kv_put/daos_kv_get with the stale pointer, which may point to
   an event still in-flight. This corrupts DAOS internal state and
   causes a SIGSEGV inside libdaos.so.

   Fix: add an explicit 'if (rc < 0) break;' guard after the inner
   spin loop, mirroring the original DAOS_EQ_WAIT code that had
   'if (rc < 0) break;' as the first check after polling.

2. Missing ev_error check in kv_put drain loop: the new NOWAIT-based
   drain loop stopped checking evp->ev_error for each drained event,
   silently ignoring I/O errors that occurred on in-flight requests.
   The original DAOS_EQ_WAIT loop checked 'rc = evp->ev_error' on
   every completion.

   Fix: restore the ev_error check in the drain loop.

Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@hpe.com>