xfs_scrub: don't return garbage value from bulkstat_the_rest

xfs_scrub: don't return garbage value from bulkstat_the_rest

bulkstat_the_rest returns an inode mask, but Codex noticed that we
carelessly return an error number if we can't allocate a bulkstat
request.  Fix this by returning 0, which forces the caller to singlestep
the rest of the bulkstat array.

Cc: linux-xfs@vger.kernel.org # v6.14.0
Fixes: 7ae92e1cb0aeeb ("xfs_scrub: try harder to fill the bulkstat array with bulkstat()")
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Andrey Albershteyn <aalbersh@kernel.org>