LU-6517 lmv: fix potential null pointer dereference

LU-6517 lmv: fix potential null pointer dereference

In lmv_disconnect_mdc do procfs removal only if we actually know the name.

Change-Id: Icb658a8a2007eea254ea5ce70b95c5d73df89914
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/14605
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>