Fix bug and remove update lock in db.instance_test_and_set()

Remove session from arguments.

Instance update works through one query, so we don't need to use update lock.

Add tests for instance_test_and_set().

blueprint db-session-cleanup

Change-Id: I143877f427f5eba4a7c7aa985bb70c79a9513822
Add API sample tests to FixedIPs extension

Partially implements blueprint nova-api-samples
Bug 1091739

Change-Id: Ie10fd85199ec10de29e99338c748f34cc04aeeb6
Merge "Add API sample tests to FixedIPs extension"
Merge "Fix bug and remove update lock in db.instance_test_and_set()"