hv_chroot: move unmount to CleanupInstance()

This allows cleanup to be done properly if the "instance" wasn't running
at all (based on the CleanupInstance framework, instead of the retry in
hypervisor).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

lib/hypervisor/hv_chroot.py

@@ -212,6 +212,13 @@ class ChrootManager(hv_base.BaseHypervisor):
         raise HypervisorError("Can't stop the processes using the chroot")
       return
 
+  def CleanupInstance(self, instance_name):
+    """Cleanup after a stopped instance
+
+    """
+    if self._IsDirLive(root_dir):
+      raise HypervisorError("Processes are still using the chroot")
+
     for mpath in self._GetMountSubdirs(root_dir):
       utils.RunCmd(["umount", mpath])