Fixed ConcurrentModificationException issue in LinkDiscovery code.

Change-Id: I2dee31353c1c0a72a69f79409f30ab6b7ad1ae73
diff --git a/providers/lldpcommon/src/main/java/org/onosproject/provider/lldpcommon/LinkDiscovery.java b/providers/lldpcommon/src/main/java/org/onosproject/provider/lldpcommon/LinkDiscovery.java
index 75458ab..735255b 100644
--- a/providers/lldpcommon/src/main/java/org/onosproject/provider/lldpcommon/LinkDiscovery.java
+++ b/providers/lldpcommon/src/main/java/org/onosproject/provider/lldpcommon/LinkDiscovery.java
@@ -68,6 +68,7 @@
 
     private Timeout timeout;
     private volatile boolean isStopped;
+
     // Set of ports to be probed
     private final HashMap<Long, String> portMap = Maps.newHashMap();
 
@@ -221,9 +222,7 @@
 
         if (context.mastershipService().isLocalMaster(device.id())) {
             log.trace("Sending probes from {}", device.id());
-            portMap.entrySet().forEach(
-                e -> sendProbes(e.getKey(), e.getValue())
-            );
+            portMap.forEach(this::sendProbes);
         }
 
         if (!isStopped()) {