Move undefining libvirt object to QubesVM class

It's more logical to do that in the QubesVM class. Moving this also
avoids protected-access pylint complain (which is very much valid
complain).

(cherry picked from commit 4643a8d)

qubes/app.py

@@ -527,15 +527,7 @@ def __delitem__(self, key):
         if not vm.is_halted():
             raise qubes.exc.QubesVMNotHaltedError(vm)
         self.app.fire_event('domain-pre-delete', pre_event=True, vm=vm)
-        try:
-            if vm.libvirt_domain:
-                vm.libvirt_domain.undefine()
-            # pylint: disable=protected-access
-            vm._libvirt_domain = None
-        except libvirt.libvirtError as e:
-            if e.get_error_code() == libvirt.VIR_ERR_NO_DOMAIN:
-                # already undefined
-                pass
+        vm.libvirt_undefine()
         del self._dict[vm.qid]
         self.app.fire_event('domain-delete', vm=vm)
 

qubes/tests/init.py

@@ -351,6 +351,9 @@ def is_halted(self):
     def get_power_state(self):
         return "Halted"
 
+    def libvirt_undefine(self):
+        pass
+
 
 class TestApp(qubes.tests.TestEmitter):
     pass

qubes/vm/qubesvm.py

@@ -1916,6 +1916,18 @@ async def clone_disk_files(self, src, pool=None, pools=None, ):
         # fire hooks
         await self.fire_event_async('domain-clone-files', src=src)
 
+    def libvirt_undefine(self):
+        """Undefine domain object in libvirt"""
+        try:
+            if self.libvirt_domain:
+                self.libvirt_domain.undefine()
+        except libvirt.libvirtError as e:
+            if e.get_error_code() == libvirt.VIR_ERR_NO_DOMAIN:
+                # already undefined
+                pass
+        if self._libvirt_domain is not None:
+            self._libvirt_domain = None
+
     #
     # methods for querying domain state
     #