ext4: correct mount option parsing to detect when quota options can be changed

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 (mount does this on
remount).

Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>