Allowed address pair: Removing check for overlap with fixed ips

Some of the overlap check has been removed in the following patch:
https://review.openstack.org/#/c/94508/
But the patch did not remove all the overlap check. I remove the
rest part.

Change-Id: I575ec54c0b3d6dc31ef80819d4258c6d162b4cfd
Closes-Bug: #1326007
Merge "Allowed address pair: Removing check for overlap with fixed ips"