Document kolla-ansible stop command

Stop command is not documented in operating-kolla.rst

Change-Id: I0f657c05c0752dcb2e6373f56af3a797967db037

doc/source/user/operating-kolla.rst

@@ -195,6 +195,8 @@ Environment.
 ``kolla-ansible -i INVENTORY check`` is used to do post-deployment smoke
 tests.
 
+``kolla-ansible -i INVENTORY stop`` is used to stop running containers.
+
 .. note::
 
    In order to do smoke tests, requires ``kolla_enable_sanity_checks=yes``.