fstests: filter mount error message for EUCLEAN and ESTALE

util-linux commit ea848180dd34 ("libmount: add
mnt_context_get_excode()") since v2.30 changed the error message on
EUCLEAN and ESTALE again (and maybe other errno too):

 - mount: <device> on <mountpoint> failed: Structure needs cleaning
 + mount: <mountpoint>: mount(2) system call failed: Structure needs cleaning.

and it causes xfs/005, overlay/037 to fail (and probably xfs/333 too,
but it's always _notrun for now).

And what's more, the mentioned tests would also fail when testing
with util-linux prior to v2.21, no one complained just because the
tests are usually _notrun on such old distributions that ship
util-linux < v2.21.

So let's filter out the changing parts and keep the error message
simple.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/overlay/037

@@ -76,12 +76,12 @@ $UMOUNT_PROG $SCRATCH_MNT
 
 # Try to mount an overlay with the same upperdir and different lowerdir - expect ESTALE
 _overlay_scratch_mount_dirs $lowerdir2 $upperdir $workdir -oindex=on \
-	2>&1 | _filter_scratch
+	2>&1 | _filter_error_mount
 $UMOUNT_PROG $SCRATCH_MNT 2>/dev/null
 
 # Try to mount an overlay with the same workdir and different upperdir - expect ESTALE
 _overlay_scratch_mount_dirs $lowerdir $upperdir2 $workdir -oindex=on \
-	2>&1 | _filter_scratch
+	2>&1 | _filter_error_mount
 $UMOUNT_PROG $SCRATCH_MNT 2>/dev/null
 
 # Mount overlay with original lowerdir, upperdir, workdir and index=on - expect success

tests/overlay/037.out

@@ -1,3 +1,3 @@
 QA output created by 037
-mount: mount SCRATCH_DEV on SCRATCH_MNT failed: Stale file handle
-mount: mount SCRATCH_DEV on SCRATCH_MNT failed: Stale file handle
+mount: Stale file handle
+mount: Stale file handle