Changing from parent_str to getting the Parent FQ name

Si is not the parent of vn.
Use parent_fq_name from si to get the project fq name.
Closes-bug: 1573979
Change-Id: I94a294eaa613c3152215a9b554f04a223c4ccf66

src/config/schema-transformer/to_bgp.py

@@ -114,9 +114,9 @@ def get_si_vns(si_obj, si_props):
         right_vn = si_props.get_right_virtual_network()
 
     if left_vn == "":
-        left_vn = parent_str + ':' + svc_info.get_left_vn_name()
+        left_vn = si_obj.get_parent_fq_name_str() + ':' + svc_info.get_left_vn_name()
     if right_vn == "":
-        right_vn = parent_str + ':' + svc_info.get_right_vn_name()
+        right_vn = si_obj.get_parent_fq_name_str() + ':' + svc_info.get_right_vn_name()
 
     return left_vn, right_vn
 # end get_si_vns