xfstests: generic/235 breaks /etc/mtab symlinks breaks xfs/189

xfstests: generic/235 breaks /etc/mtab symlinks breaks xfs/189

Serenity lost.
Insanity looms darkly.
/etc/mtab

Random behaviour.
xfs/189 fails
After a week passing.

-SCRATCH_DEV on SCRATCH_MNT type xfs (ro,filestreams)
+SCRATCH_DEV on SCRATCH_MNT type xfs (ro,relatime,attr2,filestreams,inode64,noquota)

Confusion prevails.
/proc/mounts can never give success.
Anything but golden.

ls -l
/etc/mtab shows:
lrwxrwxrwx 1 root root 12 May  8 16:05 /etc/mtab -> /proc/mounts

symlink modified.
Stealth. Deception. WTF?
Ninjas go unseen.

"git grep mtab". Yay!
generic/235: sad
SElinux hack.

Remount context grot.
Mount uses all options from
/etc/mtab

Kernel rejects mount.
sed hacks /etc/mtab
Symlink becomes file.

Test frobulation.
xfs/189 passes
Randomness tamed.

Double face-palm. Tears.
Crack-inspired insanity.
mount(8) needs fixing.

Schizophrenia.
/etc/mtab. Same thing.
Test psychiatry.

Hack, slash, glue, polish.
xfs/189 fixed.
Made shiny again.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Rich Johnston <rjohnston@sgi.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>