[PATCH] quota: improve credits estimates

Improve estimates on the number of needed credits for quota transaction.
Now we distinguish blocks that might need to be allocated and blocks that
only need to be rewritten.  Also we distinguish deleting of a quota
structure and creating of a new one.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>