init: Don't wait for ipc if corosync doesn't start

Init script now checks return code of executing corosync command. If it
fails, ipc_wait section is skipped, resulting in much faster failure of
init script.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>