remove default=None for config options

In the cfg module default=None is set as the default value.

Change-Id: I3a60876dc90a15267c51c3a3f83428896dcddced
Closes-bug: #1323975

gnocchi/storage/_carbonara.py

@@ -31,7 +31,6 @@ from gnocchi import storage
 
 OPTS = [
     cfg.IntOpt('aggregation_workers_number',
-               default=None,
                help='Number of workers to run during adding new measures for '
                     'pre-aggregation needs.'),
     cfg.StrOpt('coordination_url',

gnocchi/storage/ceph.py

@@ -32,10 +32,8 @@ OPTS = [
                default='gnocchi',
                help='Ceph pool name to use.'),
     cfg.StrOpt('ceph_username',
-               default=None,
                help='Ceph username (ie: client.admin).'),
     cfg.StrOpt('ceph_keyring',
-               default=None,
                help='Ceph keyring path.'),
     cfg.StrOpt('ceph_conffile',
                default='/etc/ceph/ceph.conf',

gnocchi/storage/swift.py

@@ -31,14 +31,12 @@ OPTS = [
                default='1',
                help='Swift authentication version to user.'),
     cfg.StrOpt('swift_preauthurl',
-               default=None,
                help='Swift pre-auth URL.'),
     cfg.StrOpt('swift_authurl',
                default="http://localhost:8080/auth/v1.0",
                help='Swift auth URL.'),
     cfg.StrOpt('swift_preauthtoken',
                secret=True,
-               default=None,
                help='Swift token to user to authenticate.'),
     cfg.StrOpt('swift_user',
                default="admin:admin",