Improve unit tests for python-quantumclient

Add tests for quantumclient.quantum.v2.quota

Partially Fixes: bug #1137783

Change-Id: I62fef9334ac864eda2f980d8ad173c536b2f3b1b
add  2.2.0 release note in index.rst file

Bug #1156480

Change-Id: Ib28266a362e76960455509b7a2af57d5315f70df
Merge "add  2.2.0 release note in index.rst file"
Merge "Improve unit tests for python-quantumclient"