node: fix secondary haproxy app fqdn

The secondary HAproxy gear in a HA application should be accessible at
the node httpd proxy via the app fqdn. Previously this extra route was
added as a sort of additional unofficial fqdn for the gear frontend that
resulted in some inconsistencies. This change updates the method used
such that the app fqdn is added as an alias on the gear frontend instead.

Bug 1155677 - HA apps add fqdn entries in frontend http configuration
causing oo-accept-node to FAIL
https://bugzilla.redhat.com/show_bug.cgi?id=1155677
Note that I didn't replace the code for the app fqdn removal case. I can do so, but I don't see when this will ever actually execute, so don't have a great way to test whether it actually works. The only time it would make sense to call this would be if an HA app was made non-HA (disable-ha event), and the haproxy cart were removed from an existing secondary proxy gear. That doesn't happen in the current implementation - HA is removed but the gear remains until scaled down, at which point the whole gear goes away along with this alias. So it didn't seem necessary to try to remove the alias with the cart.