Replace mox with mock in novaclient and compute

Replace mox with mock in tests.test_novaclient and tests.compute.test_manager.

Change-Id: Ic01fe3fd7510312e1930e87306ccc352d443fb35
Selectively import RPC backend retry config

Fixes bug 1244698

When setting the RPC publisher policies, selectively import
the retry config native to the configured RPC backend.

This avoid ImportErrors when all the dependencies of an unused
RPC backend are not installed locally.

Change-Id: If05a5a389a1b417875e0426fd83fb6d73d570487
Merge "Selectively import RPC backend retry config"
Merge "Replace mox with mock in novaclient and compute"