qubes/app: split initialising empty Qubes object from saving it

It may be useful to create fresh Qubes() object but not save it yet
before setting other things. One such case is migration from core2.

qubes/app.py

@@ -772,10 +772,7 @@ class Qubes(qubes.PropertyHolder):
         self.__load_timestamp = os.path.getmtime(self._store)
         os.close(fd_old)
 
-
-    @classmethod
-    def create_empty_store(cls, *args, **kwargs):
-        self = cls(*args, load=False, **kwargs)
+    def load_initial_values(self):
         self.labels = {
             1: qubes.Label(1, '0xcc0000', 'red'),
             2: qubes.Label(2, '0xf57900', 'orange'),
@@ -792,6 +789,11 @@ class Qubes(qubes.PropertyHolder):
 
         self.domains.add(
             qubes.vm.adminvm.AdminVM(self, None, qid=0, name='dom0'))
+
+    @classmethod
+    def create_empty_store(cls, *args, **kwargs):
+        self = cls(*args, load=False, **kwargs)
+        self.load_initial_values()
         self.save()
 
         return self