Bump the oslo-config version to address issues.

Cinder unit tests weren't running with b3, b4 has some
fixes that put things back on track.

Change-Id: I7f8b7e1ab688790577d5ea3e95b4b20c6e552fae
Better error handling around volume delete.

fixes bug 1130844

Change-Id: I6886bff24194c2ace3d7719b93b5ab79aa8a0e8d
Merge "Bump the oslo-config version to address issues."
Merge "Better error handling around volume delete."