agent: hyperstart: Implement killContainer()
agent: hyperstart: Implement killContainer()

Now that killContainer() is a new method of the agent interface,
this commit implements it for the hyperstart agent.

Signed-off-by: Sebastien Boeuf <90b401417360b1924ef3f520ddee932686110f85@intel.com>

wcwxyz/virtcontainers,wcwxyz/virtcontainers,wcwxyz/virtcontainers,containers/virtcontainers,containers/virtcontainers