Avoid cloning installed_by_rpm

qubesadmin/app.py

@@ -334,7 +334,8 @@ class QubesBase(qubesadmin.base.PropertyHolder):
             assert isinstance(dst_vm, qubesadmin.vm.QubesVM)
             for prop in src_vm.property_list():
                 # handled by admin.vm.Create call
-                if prop in ('name', 'qid', 'template', 'label', 'uuid'):
+                if prop in ('name', 'qid', 'template', 'label', 'uuid', \
+                            'installed_by_rpm'):
                     continue
                 if src_vm.property_is_default(prop):
                     continue