pacemaker: run neutron-server-start-wait-stop only at step 4

pacemaker: run neutron-server-start-wait-stop only at step 4

neutron-server-start-wait-stop is a dangerous Exec that is exposed to
race conditions, because it does not have "onlyif" or "unless"
statements.

That means during a deployment, this exec can be run in the wrong order
during Step 5 and/or 6, while it was supposed to be run at Step 4 only.
If that happens, the exec will fail because puppet tries to start
neutron-server while Pacemaker already started the resource. So in that
case, systemd would returns 1 to Puppet which would return 6 to the
overcloud deployment and the deployment would fail to finish correctly.

This patch aims to prevent from this scenario by making sure we run the
exec only during the step 4.

Also, in order to secure it a bit more, we add 'unless' statement to
this exec, so we would make sure the Puppet run would be idempotent and
the Exec would run one successful time only.

https://bugzilla.redhat.com/show_bug.cgi?id=1290582

Change-Id: I42813c5cff6c525c15c9c24baad4e355f88af672