SEBA-806:Bring up ONUs one by one

For simulating onu discovery in a frequency, a time gap inserted between the OnuDiscovery messages generated by BBSIM.
For this, the configurable IndicationInterval parameter is used.

Change-Id: I49e2afb57e8321550898cbe89ee8b17ef580dc44
diff --git a/core/api_handler.go b/core/api_handler.go
index d6c051a..8bc2c09 100644
--- a/core/api_handler.go
+++ b/core/api_handler.go
@@ -213,7 +213,7 @@
 	_ = sendDyingGaspInd(*s.EnableServer, onu.IntfID, onu.OnuID)
 	device.UpdateOnusOpStatus(onu.IntfID, onu, "down")
 	// send operstat down to voltha
-	_ = sendOnuInd(*s.EnableServer, onu, s.IndInterval, "down", "up")
+	_ = sendOnuInd(*s.EnableServer, onu, "down", "up")
 	// Give OEH some time to perform cleanup
 	time.Sleep(30 * time.Second)
 	s.activateOnu(onu)
@@ -291,7 +291,7 @@
 
 	// Send DyingGasp Alarm to VOLTHA
 	_ = sendDyingGaspInd(*s.EnableServer, onu.IntfID, onu.OnuID)
-	_ = sendOnuInd(*s.EnableServer, onu, s.IndInterval, onu.OperState, "down")
+	_ = sendOnuInd(*s.EnableServer, onu, onu.OperState, "down")
 	return nil
 }