Fixes several issues with integration tests.

* Ports and URLs used in tests are now passed from the test harness into the tests.
* The sheduler is now started with an explicit port assignment.
* The temporary rootfs from the previous run is now cleaned if it is present.
* The harness now waits until the scheduler starts responding before it launches the scheduler tests.
Stopped and running containers are now recovered upon restart rather than being killed.

Stopped containers show up in state 'created'.
Add metrics in supervisor