[cli-ref] Update python-troveclient to 2.8.0
[cli-ref] Update python-troveclient to 2.8.0

Change-Id: Id924470e4366059f6c25ab59a06cf32fac1fe558

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals