LU-1182 tests: run accounting tests when OFD is used

LU-1182 tests: run accounting tests when OFD is used

Skip all quota enforcement tests in sanity-quota.sh and only run
the accounting tests when OFD is used.

This patch also enables the ext4 quota feature when OFD is in use.
Although it is not done in a very efficient way, it still allows
us to run tests.

Signed-off-by: Johann Lombardi <johann@whamcloud.com>
Change-Id: Ie35bba9fb064acd8e878e4c31f1b43e90e164e15
Reviewed-on: http://review.whamcloud.com/3191
Tested-by: Hudson
Reviewed-by: Li Wei <liwei@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>