Add seed service destroy

This can be useful when using a seed VM that is not deployed by kayobe,
and can therefore not use ``kayobe seed deprovision``, especially when
iterating on kayobe-config during the inital stages of a deployment, or
for development, where you want to re-run the playbooks from a clean-ish
state.

Change-Id: I43a9c2a57fcfe2c9d84f39903aac7c258f9a897f