Fix test by waiting to lbaas entity delete

This fix prevents a scenario where an
lbaas entity is trying to be deleted while it still in use,
because an associate entity still didn't finished it's deletion.
Handling the DB before completing the back-end operations
can cause problems.
So waiting for back-end system response is crucial for
keeping the DB model consistent.

A new network timeout and time interval options were
added in configuration file. These were added to give control over
network resources wait periods without effecting other projects.

Added wait_for_resource_deletion and is_resource_deleted functions,
similar to the common rest_client functions but with resource type
as a parameter since network service has no rest_client for each resource.
calling the new function when deleting vips and pools.

Bug #1288326 was opened to address the fact that network rest client does
not fit common REST client framework approach where each resource
has its own implementation of the client.

This change is a replacement for the change below.
https://review.openstack.org/#/c/68190/3
Was replaced due to a development workstation crash.

Change-Id: Ie6468f0488ea2515ed8ccbe1a8c9c55b9ab4a3de
Closes-Bug: #1271214
4 files changed