Set default pool value to system in gpfs driver

The configuration option gpfs_storage_pool is assigned with
default value of None. And it gets initialized with None
instead of system, where as the intention is to set the default
value as system.

This change sets default value of gpfs_storage_pool to system
instead of None.

DocImpact

Needs an update in gpfs driver documentation, as this patch
proposes a change in default value of configuration option
(gpfs_storage_pool)

Change-Id: Ib4c2a2e4593a940ae563d329fd59d2d5fe3d4520
Closes-Bug: #1365474

cinder/volume/drivers/ibm/gpfs.py

@@ -73,9 +73,9 @@
                       'volume is created as a fully allocated file, in which '
                       'case, creation may take a significantly longer time.')),
     cfg.StrOpt('gpfs_storage_pool',
-               default=None,
+               default='system',
                help=('Specifies the storage pool that volumes are assigned '
-                     'to.  By default, the system storage pool is used.')),
+                     'to. By default, the system storage pool is used.')),
 ]
 CONF = cfg.CONF
 CONF.register_opts(gpfs_opts)
@@ -333,7 +333,7 @@ def do_setup(self, ctxt):
             raise exception.VolumeBackendAPIException(data=msg)
 
         pool = self.configuration.safe_get('gpfs_storage_pool')
-        self._storage_pool = pool or 'system'
+        self._storage_pool = pool
         if not self._verify_gpfs_pool(self._storage_pool):
             msg = (_('Invalid storage pool %s specificed.') %
                    self._storage_pool)

etc/cinder/cinder.conf.sample

@@ -1399,9 +1399,9 @@
 # may take a significantly longer time. (boolean value)
 #gpfs_sparse_volumes=true
 
-# Specifies the storage pool that volumes are assigned to.  By
+# Specifies the storage pool that volumes are assigned to. By
 # default, the system storage pool is used. (string value)
-#gpfs_storage_pool=<None>
+#gpfs_storage_pool=system
 
 
 #