Add LazyPluggable utility from nova.

This commit merges in the LazyPluggable utility
from nova in to glance.common.utils. This is required
for the new test_migrations framework.

Change-Id: Ic9520db3f11f13e1a83882101980fcaaacc73729
Fix version issue during nosetests run

Pick up the latest files from oslo

Fixes LP# 1118845

Change-Id: I1c9a19508fc18f18936624fa233d3fdc6d31e43f
Merge "Add LazyPluggable utility from nova."
Merge "Fix version issue during nosetests run"