Fix secrets for cinder-on-ceph

The /etc/ceph/secret.xml file is currently malformed due to a
missing variable.  We're also not using the UUID generated
from the secret in cinder.conf like we should.  This
fixes both issues.
Rename variables to be less confusing

The variables in uuid_injection refer to a key when
what we're really after is a uuid.  They are not
the same thing.
Merge pull request #7 from markvoelker/grizzly

Fix secrets for cinder-on-ceph