[DLM] Telnet to port 21064 can stop all lockspaces

This patch fixes Red Hat bz#245892

Opening a tcp connection from a cluster member to another cluster member
targeting the dlm port it is enough to stop every dlm operation in the cluster.
This means that GFS and rgmanager will hang.

Signed-Off-By: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>