mgr: install tox==2.9.1 for tox tests

mgr: install tox==2.9.1 for tox tests

* pybind/mgr/ansible/requirements.txt:
  in src/pybind/mgr/ansible/tox.ini, tox>=2.8.1 is required. to be
consistent with other requirements.txt in Ceph, tox 2.9.1 will be
installed for these tox environments.
* pybind/mgr/orchestrator_cli/requirements.txt:
  in src/pybind/mgr/orchestrator_cli: tox>=2.5 is required. to be
consistent with other requirements.txt in Ceph, tox 2.9.1 will be
installed for these tox environments.

Signed-off-by: Kefu Chai <kchai@redhat.com>