cfgtool: Remove unused code

corosync_cfg_ring_status_get returns string status, which is always OK
for UDP(U) and detailed status for Knet transport. Previously also
FAULTY status was returned for UDP(U) and cfgtool used to return error
code back to shell when one of the interfaces was faulty.

Because FAULTY is now not returned, it's not needed to have code for
handling it.

Also man page was misleading, so it is fixed too.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>