cinder.backup: Replace 'locals()' with explicit values

Help bring source code into compliance with the Cinder Style Commandments:
https://github.com/openstack/cinder/blob/master/HACKING.rst

This change covers all affected source in the cinder backup module, i.e.
cinder/backup/*.py and subdirectories.

Partially fixes: bug #1190748

Change-Id: I3e0f3806030f1813d055135f15e64b5a719970ed
Merge "cinder.backup: Replace 'locals()' with explicit values"