Stop abusing pacemaker groups

[vuntz]

Groups come with ordering constraints which don't make sense. Historically, the groups have been used mostly for convenience -- but that's not a good enough reason. It has been shown that restarting the neutron dhcp agent can result in temporary network outage because of the groups.

This was done for master: crowbar#799

Needs backporting, which is slightly challenging to do without outage.

[matelakat]

needs backport