The check is superfluous since all callers who set search_for_commit
also have skip_locking set.

ASSERT() is put in place to ensure skip_locking is set by new callers.
Reviewed-by: NQu Wenruo <wqu@suse.com>
Signed-off-by: NLiu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>