fs: dlm: don't close socket on invalid message

This patch doesn't close sockets when there is an invalid dlm message
received. The connection will probably reconnect anyway so. To not
close the connection will reduce the number of possible failtures.
As we don't have a different strategy to react on such scenario
just keep going the connection and ignore the message.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>