drbd83: add dependency for rhel-6.6 kernel

Signed-off-by: Philip J Perry <phil@elrepo.org>
drbd83: Backport flush_signals() before kthread_run() fix

See http://elrepo.org/bugs/view.php?id=533

Committed-by: Madison Kelly <mkelly@alteeve.ca>
Signed-off-by: Philip J Perry <phil@elrepo.org>