properly format error messages for volume resizing
properly format error messages for volume resizing

The error messages are tuples and not substituting variables.

Before:
$ openstack volume set vol1 --size 1
Failed to set volume size: (u'New size must be greater than %s GB', 2)

$ openstack volume set vol1 --size 1
Failed to set volume size: (u'Volume is in %s state, it must be available
before size can be extended', u'error')

After:
$ openstack volume set vol2 --size 3
Failed to set volume size: New size must be greater than 4 GB

$ openstack volume set vol2 --size 3
Failed to set volume size: Volume is in error state, it must be available
before size can be extended

Change-Id: Ide6e644b1c6d1c11a9dc2f3f53c1a1837380b8d5

openstack/python-openstackclient,openstack/python-openstackclient,dtroyer/python-openstackclient,dtroyer/python-openstackclient