LU-2222 mdt: restore evict-by-nid functionality

LU-2222 mdt: restore evict-by-nid functionality

Writing a NID or UUID to mdt.*.evict_tgt_nids will evict clients
with NID or UUID specified all the targets (OSTs and MDTs).

Change-Id: I66a60a6c81fbac1571f5685111df7b00a306be36
Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-on: http://review.whamcloud.com/16867
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>