LU-1842 test: re-enable all sanity-quota tests

This patch enables all sanity-quota tests that were disabled in order
to land the new quota architecture (based on qsd/qmt). All those
tests should now pass.

This patch also reduces the time it takes to run test 6 (it used to
sleep for at_max = 600s).

Signed-off-by: Johann Lombardi <johann.lombardi@intel.com>
Change-Id: Idac4812663a3c90a213cc59d03b5f28f561ac39d
Reviewed-on: http://review.whamcloud.com/4200
Tested-by: Hudson
Reviewed-by: Jinshan Xiong <jinshan.xiong@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>