This fixes the iptables rules generated by the L3 agent
(SNAT, DNAT, set-mark and metadata), and the DHCP agent
(checksum-fill) to match the format that will be returned
by iptables-save to prevent excessive extra replacement
work done by the iptables manager.
It also fixes the iptables test that was not passing the
expected arguments (-p PROTO -m PROTO) for block rules.
A simple test was added to the L3 agent to ensure that the
rules have converged during the normal lifecycle tests.
Closes-Bug: #1566007
Change-Id: I5e8e27cdbf0d0448011881614671efe53bb1b6a1
(cherry picked from commit b8d520ffe2)