LU-9452 ldlm: remove MSG_CONNECT_LIBCLIENT support

LU-9452 ldlm: remove MSG_CONNECT_LIBCLIENT support

Remove old server code that handled liblustre client connections,
marked with MSG_CONNECT_LIBCLIENT and associated code checking for
exp_libclient.  Servers will now outright refuse connections from
liblustre clients with a clear message, rather than allowing the
connection and pretending to work.  Liblustre client support was
broken and removed years ago.

There are still some liblustre remnants in the code (e.g. blocked
lock handling for LDLM_FL_CANCEL_ON_BLOCK), but that has more
complex semantics and should be removed in a separate patch.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Ifbea507e82d758f849db24094c5cc0a8003ebbe5
Reviewed-on: https://review.whamcloud.com/26972
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>