Properly set up SIS when cloning course instance

Fixes apluslms#1177.

Author: PasiSa

edit_course/operations/clone.py

@@ -80,6 +80,8 @@ def clone( # pylint: disable=too-many-locals too-many-arguments
     instance.configure_url = ""
     instance.url = url
     instance.instance_name = name
+    instance.sis_id =''
+    instance.sis_enroll = False
     instance.save()
 
     if clone_teachers: