Remove unused Task classes
Remove unused Task classes

We haven't used these in a while, but they got missed in the patch that
removed their use.

Change-Id: Ic1ce458942b131aa1c72ee1a85d0688d1883a5cc

dtroyer/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk,dtroyer/python-openstacksdk