Add a QuotaClient and quota API tests

This change adds a QuotaClient for testing the Barbican quota API.
It adds a quota test suite and integrates the QuotaClient with the
plugin testing infrastructure.

Change-Id: I3249fb879f519da63129e0ec5117377a21094974
Depends-On: I813648476a3a7b0b0e416a524d4629dffe36c92e
Implements: bp tempest-plugin
diff --git a/barbican_tempest_plugin/plugin.py b/barbican_tempest_plugin/plugin.py
index a0f4ca4..2c13b24 100644
--- a/barbican_tempest_plugin/plugin.py
+++ b/barbican_tempest_plugin/plugin.py
@@ -45,6 +45,7 @@
                 'ConsumerClient',
                 'ContainerClient',
                 'OrderClient',
+                'QuotaClient',
                 'SecretClient',
                 'SecretMetadataClient'
             ],