dlm: release socket on error

It seems that `sock' allocated by sock_create_kern in
tcp_connect_to_sock() of dlm/fs/lowcomms.c is not released if
dlm_nodeid_to_addr an error.

Acked-by: Christine Caulfield <ccaulfie@redhat.com>
Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>