[VOL-3929] Fix for bbsim restart on grpc server restart followed by a device disable/delete

Change-Id: I47902c8a94b481933d2b14bb2530124523622046
diff --git a/internal/bbsim/devices/olt.go b/internal/bbsim/devices/olt.go
index b2c82d9..f6a4b40 100644
--- a/internal/bbsim/devices/olt.go
+++ b/internal/bbsim/devices/olt.go
@@ -49,7 +49,7 @@
 
 type OltDevice struct {
 	sync.Mutex
-	oltServer *grpc.Server
+	OltServer *grpc.Server
 
 	// BBSIM Internals
 	ID                   int
@@ -226,8 +226,8 @@
 
 func (o *OltDevice) InitOlt() {
 
-	if o.oltServer == nil {
-		o.oltServer, _ = o.StartOltServer()
+	if o.OltServer == nil {
+		o.OltServer, _ = o.StartOltServer()
 	} else {
 		oltLogger.Fatal("OLT server already running.")
 	}
@@ -355,12 +355,12 @@
 
 // StopOltServer stops the OpenOLT grpc server
 func (o *OltDevice) StopOltServer() {
-	if o.oltServer != nil {
+	if o.OltServer != nil {
 		oltLogger.WithFields(log.Fields{
 			"oltId": o.SerialNumber,
 		}).Warnf("Stopping OLT gRPC server")
-		o.oltServer.Stop()
-		o.oltServer = nil
+		o.OltServer.Stop()
+		o.OltServer = nil
 	}
 }