LU-3731 ldlm: Fix misleading error message

LU-3731 ldlm: Fix misleading error message

This is a correct error when target only mounts on one server,
but is a misleading error message for an HA scenario.

This rebased patch makes the error message a little clearer for
admins running in HA.

Signed-off-by: Bobbie Lind <bobbie.j.lind@intel.com>
Change-Id: I4bdc7891812dd5db65a4dff420632b771a97d103
Reviewed-on: http://review.whamcloud.com/7438
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Tested-by: Hudson
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>