Wait for resource deletion after 202 response. Fixes bug 1007447.

Added RestClient.wait_for_resource_deletion that waits for a subclass-specific condition.
Added RestClient.is_resource_deleted that implements a subclass-specific deletion predicate.
Removed redundant test by combining floating_ip associate/dissacociate into a single test.

Change-Id: Iac043b12e8d5a5e88786e3b573280bfbc3f6a8d6
6 files changed