Error message is malformed when removing a sec group from an instance

In the current code the Error message string for a security group which is not
associated with an instance does not get expanded correctly, resulting in users
getting a message:

ERROR: [u'Security group %(security_group_name)s not assocaited with the
instance %(instance)s', {u'instance': u'71069945-5bea-4d53-b6ab-9026bfeebba4',
u'security_group_name': u'phil'}]

In addition fix a minor typo in this message, and clean up a few cases where
error messages are not being passed through _() for i18n.

Change-Id: I85856a135a62bc3415a355e0900ea12ea55f73ae
Closes-Bug: #1273266
Merge "Error message is malformed when removing a sec group from an instance"