quota: fix disabling quota, add quota tests

Update all superblock copies when disabling the quota feature.

Added basic tests for the quota feature.

Signed-off-by: Niu Yawei <niu@whamcloud.com>
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
10 files changed