RadosClient: Fixing potential lock leaks.

In lookup_pool and pool_delete, a lock is taken
before invoking wait_for_osdmap, but is not
released for the failure case of the call. Fixing the same.

Fixes: #9022
Signed-off-by: Pavan Rallabhandi <pavan.rallabhandi@sandisk.com>
EC-ISA: add intelligent table cache