LU-4571 fld: resend seq lookup RPC if it is on LWP

Because Light Weight connection might be evicted after
restart, then cause inflight RPC fails, to avoid this,
we need resend seq lookup RPC.

remove "-f" from "stop mdt" in sanity 17m, so umount can
keep the the connection, and otherwise the OSP might be
evicted.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I032dfb95e65da56b198129c6d6d6039bad08ab9c
Reviewed-on: http://review.whamcloud.com/9106
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>