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/grpc_service.go b/core/grpc_service.go
index 8e9e122..8ac0faf 100644
--- a/core/grpc_service.go
+++ b/core/grpc_service.go
@@ -112,7 +112,7 @@
 	matched.OnuID = onuid
 	s.updateDevIntState(matched, device.ONU_ACTIVE)
 	logger.Debug("ONU IntfID: %d OnuID: %d activated succesufully.", onu.IntfId, onu.OnuId)
-	if err := sendOnuInd(*s.EnableServer, matched, s.IndInterval, "up", "up"); err != nil {
+	if err := sendOnuInd(*s.EnableServer, matched, "up", "up"); err != nil {
 		logger.Error("Failed to send ONU Indication intfID %d, onuID %d", matched.IntfID, matched.OnuID)
 		return new(openolt.Empty), err
 	}