Fix saving machine instances to the cura profile

CURA-340, see https://github.com/Ultimaker/Cura/commit/c79b7bdd7ad2ed7df481f718c87346a489ba5da9

cura/CuraApplication.py

@@ -271,7 +271,7 @@ class CuraApplication(QtApplication):
             file_name = urllib.parse.quote_plus(stack.getId()) + ".stack.cfg"
             stack_type = stack.getMetaDataEntry("type", None)
             path = None
-            if not stack_type:
+            if not stack_type or stack_type == "machine":
                 path = Resources.getStoragePath(self.ResourceTypes.MachineStack, file_name)
             elif stack_type == "extruder":
                 path = Resources.getStoragePath(self.ResourceTypes.ExtruderStack, file_name)