Add a --marker argument to the backup commands.
Add a --marker argument to the backup commands.

The backup commands provided a limit but no --marker argument.

Change-Id: I6982172acb3eadfc5ef51dc81c0d2cf666272801
Closes-Bug: #1461603

openstack/python-troveclient,Tesora/tesora-python-troveclient,openstack/python-troveclient,Tesora/tesora-python-troveclient