Remove NotImplementedError exception
Remove NotImplementedError exception

get_default_vim function is already implemented, hence we should change
'NotImplementedError' to 'pass' statement

Change-Id: I6511fd9d5cb3d33edee61253de2563a1416955d3

openstack/tacker,stackforge/tacker,stackforge/tacker,openstack/tacker,openstack/tacker