Merge ~ack/maas:1905263-lxd-delete-force-2.9 into maas:2.9

[Alberto Donato]

LP: #1905263 - force-stop LXD VMs when decomposing, and wait for them to be stopped before removing

[Alberto Donato (ack)]

review: Approve

diff --git a/src/provisioningserver/drivers/pod/lxd.py b/src/provisioningserver/drivers/pod/lxd.py
index ad9c129..bcb3e68 100644
--- a/src/provisioningserver/drivers/pod/lxd.py
+++ b/src/provisioningserver/drivers/pod/lxd.py
@@ -704,12 +704,13 @@ class LXDPodDriver(PodDriver):
     def decompose(self, pod_id, context):
         """Decompose a virtual machine."""
         client = yield self.get_client(pod_id, context)
-        machine = yield deferToThread(
-            client.virtual_machines.get, context["instance_name"]
-        )
-        # Stop the machine.
-        yield deferToThread(machine.stop)
-        yield deferToThread(machine.delete, wait=True)
+
+        def sync_decompose(instance_name):
+            machine = client.virtual_machines.get(instance_name)
+            machine.stop(force=True, wait=True)
+            machine.delete(wait=True)
+
+        yield deferToThread(sync_decompose, context["instance_name"])
         # Hints are updated on the region for LXDPodDriver.
         return DiscoveredPodHints()
 
diff --git a/src/provisioningserver/drivers/pod/tests/test_lxd.py b/src/provisioningserver/drivers/pod/tests/test_lxd.py
index c406763..99f53d9 100644
--- a/src/provisioningserver/drivers/pod/tests/test_lxd.py
+++ b/src/provisioningserver/drivers/pod/tests/test_lxd.py
@@ -1046,7 +1046,9 @@ class TestLXDPodDriver(MAASTestCase):
         client.virtual_machines.get.return_value = mock_machine
         empty_hints = yield driver.decompose(pod_id, context)
 
-        self.assertThat(mock_machine.stop, MockCalledOnceWith())
+        self.assertThat(
+            mock_machine.stop, MockCalledOnceWith(force=True, wait=True)
+        )
         self.assertThat(mock_machine.delete, MockCalledOnceWith(wait=True))
         self.assertThat(
             empty_hints,