CARP stopped working after upgrade from 11 to 12

[Pete French]

> I have confirmed that pfsync is the culprit. Read on for details.

Excellent work. I;m home now, so won't get a chnace to out this into
practice until tomorrow unfortunately, but it's brilliant that you have
confirmed it.

> I tried disabling pfsync and rebooting both nodes, they came up as 
> MASTER/SLAVE then.

This is very useful to know - I willprobably  try tomorrow running my
firewalls back up with pfsync disabled to see if it works for me too.

> Then I tried enabling pfsync and starting it, and on the SLAVE node I 
> immediately got:

That kind of confirms it really doesnt it ?

So, is it possible to get r342051 backend out of STABLE for now ? This
is a bit 'gotcha' for anyone running a firewall pair with CARp after all.

-pete.

PS: are you going to file a PR ?