LU-15207 libcfs: reset hs_rehash_bits

LU-15207 libcfs: reset hs_rehash_bits

if rehash work is cancelled, then nobody resets
hs_rehash_bits and the first iterator asserts
at LASSERT(!cfs_hash_is_rehashing(hs)) in
cfs_hash_for_each_relax().

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I1a567f6be77ca6c45e5d4f256722206b12588554
Reviewed-on: https://review.whamcloud.com/45533
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>