Fix `openstack cluster event list` bug
Fix `openstack cluster event list` bug

Before this patch, `openstack cluster event list` can't list events.
Closes-Bug:#1622587

Change-Id: Ia47f619a5e2349977076eb6be96ad146907af555

openstack/python-senlinclient,stackforge/python-senlinclient,openstack/python-senlinclient,stackforge/python-senlinclient