Fixed deadlock in the task_group conforance tests (#699)
Fixed deadlock in the task_group conforance tests (#699)

- use same arena for task_group::run() and task_group::wait() methods
- use single thread environment for test stability

Signed-off-by: Anton Potapov <46a4e7c6e329e26e2944dd3051648ee305c41419@intel.com>
oneapi-src/oneTBB,oneapi-src/oneTBB,oneapi-src/oneTBB,oneapi-src/oneTBB