do not raise exception on ip address recycle operation

Currenty a exception will raise on ip address recycle operation if the ip
address doesn't belong to any allocation pool which will make user unable
to update port, even worse it will make user unable to create new port.
So do not raise exception if the ip address to be recycled doesn't belong
to any allocation, just delete it from the ip allocation table.

fixes bug 1201692

Change-Id: Icfbded5158f1f4043f69bb1463fd4c830c9714a9
Merge "do not raise exception on ip address recycle operation"