Add copyright text to glance/openstack/common/__init__.py

Synchronize the content of glance/openstack/common/__init__.py to the
one in oslo-incubator.

Change-Id: Idd059e3f4d00d91c9a14cf302fd780044929e3e5
Closes-bug: #1288877
Make the VMware datastore backend more robust

This patch contains several fixes related to invalid configurations
and corner cases:
- better error handling for the store operations
- better logging when response is not successful
- better support for various store_image_dir formats

Change-Id: I6c0003e29d621c1f71490cb9fce163dc840a113f
Closes-Bug: #1291646
Merge "Add copyright text to glance/openstack/common/__init__.py"