Openvswitch update_port should return updated port info

Found when I enabled test_extension_allowedaddress_pairs, where
test_create_port_removed_allowed_address_pairs would fail due to the
returned port still containing the original addresspair.  The cause is
ovs simply not updating the port info being returned.

This patch additionally enables test_extension_allowedaddress_pairs for
openvswitch.

Moved checks and updating into method similar to what we do for
extradhcpopts and security_groups.

Additionally, this required fixing is_address_pairs_attribute_updated() as
it was passing (non-hashable) dicts to utils.compare_elements.

Change-Id: Ic871fea68fb9fcc862b1fd5ae5fe7aec540e4a30
Partial-Bug: #1255150
Merge "Openvswitch update_port should return updated port info"