Tests that call host.backend.get_hostname() to switch on test
assertions are likely to fail open. Stop using this in zuul tests
and instead add new files for each of the types of zuul hosts
where we want to do additional verification.
Share the iptables related code between all the tests that perform
iptables checks.
Also, some extra merger test and some negative assertions are added.
Move multi-node-hosts-file to after set-hostname. multi-node-hosts-file
is designed to append, and set-hostname is designed to write.
When we write the gate version of the inventory, map the nodepool
private_ipv4 address as the public_v4 address of the inventory host
since that's what is written to /etc/hosts, and is therefore, in the
context of a gate job, the "public" address.
Change-Id: Id2dad08176865169272a8c135d232c2b58a7a2c1
