Allowed Addresspairs: Removing check for overlap with fixed ips

Current code does not allow assigning a fixed ip to a port when that ip
overlaps with one of the addresses in the allowed-addresspairs list.
This is an unnecessary check as the overlap does not have any negative
effect. Further, such a check actually makes it hard to use this
API. For example, if a fixed IP 10.10.1.1 exists on a port and we
want to allow addresses in 10.10.1.0/24 cidr on that port, then one
has to configure a list of 8 cidrs ([10.10.1.0/32, 10.10.1.2/31,
10.10.1.4/30, ..., 10.10.1.128/25]) on the allowed-addresspairs.
In addition to the above reasons, the current code also does not
check for the overlaps in all cases.

This patch summarily removes this overlap check.

Closes-Bug: #1321864
Change-Id: I5498c4a72b31267644da10a54a9860c1fc3bb250
Merge "Allowed Addresspairs: Removing check for overlap with fixed ips"