If task has contexts.quotas, it runs quotas cleanup after running test. And if running with existing_users, save tenants' quota at setup and restore after the running, while quotas cleanup. But checking existing users in context does not work well. This commit checks correctly that existing_users key is in context.
Closes-Bug: #2119493
Change-Id: Id67722296294a10abe7f3b83badd8b586734a709
Signed-off-by: eunkyung <ek121.kim@samsung.com>