Fix resource leakage in messaging.test_queues

Test messaging.test_queues.test_delete_queue does pop 1 element from
shared list (self.queues which is being used by other tests as well
as in resource cleanup) and then delete request is done.

In case where delete request fails then it cause other tests to fail
and resource leakage as element has been removed from self.queues
even before actual deletion.

Individual test should not be side-effecting mutable class variables
that are used by other tests. So merging delete tests with create tests.

Closes-Bug: #1377031

Change-Id: If24a903160e716a685d7121e0968881542f072fc