This change adds database support for the python-openstackclient
project for the cluster-instances command.
The trove command cluster-instances is now:
openstack database cluster list instances
Change-Id: Ifcbb0a0374d4b2918ee22b85a0733c8bbbf21497
Partially-Implements: blueprint trove-support-in-python-openstackclient
Signed-off-by: Zhao Chao <zhaochao1984@gmail.com>