fix 1187 create notification task with the proper loop

Also call notifications when there are subscribers

Change-Id: Icf6b4f88aaf633282c2736de85803f845b17d4c6
Signed-off-by: tierno <alfonso.tiernosepulveda@telefonica.com>
diff --git a/osm_nbi/subscriptions.py b/osm_nbi/subscriptions.py
index c6105ee..ec70d0c 100644
--- a/osm_nbi/subscriptions.py
+++ b/osm_nbi/subscriptions.py
@@ -201,7 +201,9 @@
                                                                      event_details)
                             # self.logger.debug("subscribers list: ")
                             # self.logger.debug(subscribers)
-                            asyncio.ensure_future(self.nslcm.send_notifications(subscribers, loop=self.loop))
+                            if subscribers:
+                                asyncio.ensure_future(self.nslcm.send_notifications(subscribers, loop=self.loop),
+                                                      loop=self.loop)
                 else:
                     self.logger.debug("Message can not be used for notification of nslcm")
             elif topic == "nsi":