We should not allow user to change quota mount options when quota is just
suspended.  It would make mount options and internal quota state inconsistent.

Also we should not allow user to change quota format when quota is turned on.
On the other hand we can just silently ignore when some option is set to the
value it already has (some mount versions do this on remount).  Finally, we
should not discard current quota options if parsing of mount options fails.

Cc: <reiserfs-devel@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>