LU-5777 quota: reserve enough credits for setattr

On chown/chgrp operation, the file to be changed could be the
last file of owner/group, and the user/group ID entry could be
removed from the quota file in this setattr operation. We'd
reserve enough journal credits for such case.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Change-Id: Ida22092739a6380cca0d6eccc45e1f06f5e82adb
Reviewed-on: http://review.whamcloud.com/12361
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>