Adds a flag to allow configuring a region

If multiple regions contain an endpoint, extract
the correct endpoint URL from the os_region_name parameter
in nova.conf

Fixes LP Bug #1087735

Change-Id: Id4e4f56f336cd2b092a173b3c8e695b173c76f2a
Correct docstring on sizelimit middleware.

Change-Id: I6b20080c4f0b144264dfbaf9e73a779b5c9baed9
Merge "Adds a flag to allow configuring a region"
Merge "Correct docstring on sizelimit middleware."