LU-11843 tests: customise sanity-quota

LU-11843 tests: customise sanity-quota

Patch adds the possibility to not turn project quotas OFF
at the end of sanity-quota if it is ON initially.
ENABLE_PROJECT_QUOTA=false is ignored in this case.

Signed-off-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-6162
Reviewed-by: Alexander Boyko <c17825@cray.com>
Reviewed-by: Vladimir Saveliev <c17830@cray.com>
Test-Parameters: trivial testlist=sanity-quota
Change-Id: Ic7d58f4a077acdbeec426613777e3c7c0778f0a0
Reviewed-on: https://review.whamcloud.com/33997
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandr Boyko <c17825@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>