LU-5695 libcfs: watchdog dispatch thread fix

LU-5695 libcfs: watchdog dispatch thread fix

lc_watchdogd may stop imediately after start
because nobody clears the stop flag.

Xyratex-bug-id: MRP-2108 MRP-1913
Change-Id: I1eaaf0330c111b7f2b17081c716ef8c200677d6b
Signed-off-by: Alexander Zarochentsev <alexander.zarochentsev@seagate.com>
Reviewed-on: https://review.whamcloud.com/12155
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>