dlm: fix socket fd translation

The code to set up sctp sockets was not using the sockfd_lookup()
and sockfd_put() routines to translate an fd to a socket.  The
direct fget and fput calls were resulting in error messages from
alloc_fd().

Also clean up two log messages and remove a third, related to
setting up sctp associations.

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