Merge "Allow update of ext gateway IP's w/out port delete"

diff --cc neutron/db/l3_db.py
Simple merge

diff --cc neutron/db/l3_dvr_db.py
Simple merge

diff --cc neutron/tests/unit/db/test_l3_dvr_db.py
Simple merge

diff --cc neutron/tests/unit/test_l3_plugin.py
Simple merge