VOL-4491 add pon-port label to the context of olt_los indication

Change-Id: I09a43753c9427a131650112127b15576994ab58f
diff --git a/internal/pkg/core/openolt_eventmgr.go b/internal/pkg/core/openolt_eventmgr.go
index a3bf003..971a173 100644
--- a/internal/pkg/core/openolt_eventmgr.go
+++ b/internal/pkg/core/openolt_eventmgr.go
@@ -305,6 +305,7 @@
 	context := make(map[string]string)
 	/* Populating event context */
 	context[ContextOltPonIntfID] = strconv.FormatUint(uint64(ponIntdID), base10)
+	context[ContextOltPortLabel], _ = GetportLabel(oltLos.IntfId, voltha.Port_PON_OLT)
 	/* Populating device event body */
 	de.Context = context
 	de.ResourceId = deviceID