Merge v1_1's base module into main base module

This class was forked from novaclient.base when adding v1.1 support and
and because v1.0 is no longer supported it can be merged again.

blueprint: improve-block-device-handling

Change-Id: I3113eff522a9dc280f48053001afa9e1a0cad3e3
Merge "Merge v1_1's base module into main base module"