LU-10419 lfsck: signal master engine when stop

LU-10419 lfsck: signal master engine when stop

It is possible that during the LFSCK scanning, some server, MDT
or OST, maybe offline. At that time, if the LFSCK needs to talk
with such offline server, related RPC will trigger reconnect to
the offline server, and the LFSCK engine has to wait untill the
offline server become online or someone deactives the server by
force. To avoid being blocked when lfsck_stop() under such case,
the stop logic will send SIGINT signal to LFSCK engines. But we
only do that for the LFSCK assistant engines, forget to do that
for the LFSCK master engine. This patch fixes that.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I5d51ab49524e8ae54f0853e93b94e78913f65e8a
Reviewed-on: https://review.whamcloud.com/31627
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>