Improve unit tests for python-glanceclient.glanceclient.common.base

Add several tests for glanceclient.common.base module

Fixes: bug #1144158
Change-Id: Ifc288075c79849ee1384f09f513874ee08cd0248
Migrate to flake8.

Fixes bug 1172444.

Change-Id: Icec0820d0f780ed9473218b7e46e29c1e3db6541
Migrate to pbr.

Fixes bug 1179007.

Change-Id: I99d571bbf37ef53366a96de088c249cb6fd23b0e
Merge "Improve unit tests for python-glanceclient.glanceclient.common.base"
Merge "Migrate to flake8."
Merge "Migrate to pbr."