LU-1267 lfsck: enhance RPCs (1) for MDT-OST consistency

LU-1267 lfsck: enhance RPCs (1) for MDT-OST consistency

Introduce new RPC LFSCK_NOTIFY for the LFSCK instance on the server_1
to notify the LFSCK instance on the server_2 about the event such as:
lfsck start/stop/pause/fail/phaseX_done, and so on.

Introduce new RPC LFSCK_QUERY for the LFSCK instance on the server_1
to query the LFSCK status on the server_2.

The two new RPCs are used not only for MDT-OST consistency, but also
for DNE consistency in the future.

Test-Parameters: allwaysuploadlogs
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I8529f1a3f5f7f9589101f456f0397c8ebe11df18
Reviewed-on: http://review.whamcloud.com/8623
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>