When LB or member is created, driver looks for the Logical Router which
is plugged to the Logical Switch. As there can be more than one address
on the port, we should iterate over them to be compared with the gateway
IP.
This patch modifies code to do not crash if more than one address is
found in neutron:cidrs external_ids field.
Closes-Bug: 2036620
Change-Id: I17b2c2577a4d99455c30ca1e10632a7004d7c084