Add ContainerStateExited and OCI delete() in cleanup()

To work better with Kata containers, we need to delete() from the
OCI runtime as a part of cleanup, to ensure resources aren't
retained longer than they need to be.

To enable this, we need to add a new state to containers,
ContainerStateExited. Containers transition from
ContainerStateStopped to ContainerStateExited via cleanupRuntime
which is invoked as part of cleanup(). A container in the Exited
state is identical to Stopped, except it has been removed from
the OCI runtime and thus will be handled differently when
initializing the container.

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

pkg/varlinkapi/pods.go

@@ -125,7 +125,7 @@ func (i *LibpodAPI) StopPod(call iopodman.VarlinkCall, name string) error {
 	if err != nil {
 		return call.ReplyPodNotFound(name)
 	}
-	ctrErrs, err := pod.Stop(true)
+	ctrErrs, err := pod.Stop(getContext(), true)
 	callErr := handlePodCall(call, pod, ctrErrs, err)
 	if callErr != nil {
 		return err