Update ns.py to fix import of osm_common version

Change-Id: I7e0e30114ebb9d80813ba8470efdc41b9f48087e
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>
diff --git a/NG-RO/osm_ng_ro/ns.py b/NG-RO/osm_ng_ro/ns.py
index 995ad5b..5791e88 100644
--- a/NG-RO/osm_ng_ro/ns.py
+++ b/NG-RO/osm_ng_ro/ns.py
@@ -39,7 +39,6 @@
     UndefinedError,
 )
 from osm_common import (
-    _version as common_version,
     dbmemory,
     dbmongo,
     fslocal,
@@ -47,6 +46,7 @@
     msgkafka,
     msglocal,
 )
+from osm_common._version import version as common_version
 from osm_common.dbbase import DbBase, DbException
 from osm_common.fsbase import FsBase, FsException
 from osm_common.msgbase import MsgException