LU-13358 libcfs: add timeout to cfs_race() to fix race

LU-13358 libcfs: add timeout to cfs_race() to fix race

there is no guarantee for the branches in cfs_race() to be executed
in strict order, thus it's possible that the second branch (with
cfs_race_state=1) is executed before the first branch and then another
thread executing the first branch gets stuck.

this construction is used for testing only and as a
workaround it's enough to timeout.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Ie1cc0accedb3e1a198d4b17d1ab00ce298c560f2
Reviewed-on: https://review.whamcloud.com/43161
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Neil Brown <neilb@suse.de>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>