Fix ONOS-4683 - Don't process device events on the listener thread

Change-Id: Icc465311c2c047dba11bacc69c745bbda55ea714
diff --git a/providers/lldp/src/test/java/org/onosproject/provider/lldp/impl/LldpLinkProviderTest.java b/providers/lldp/src/test/java/org/onosproject/provider/lldp/impl/LldpLinkProviderTest.java
index fb1bf67..811baac 100644
--- a/providers/lldp/src/test/java/org/onosproject/provider/lldp/impl/LldpLinkProviderTest.java
+++ b/providers/lldp/src/test/java/org/onosproject/provider/lldp/impl/LldpLinkProviderTest.java
@@ -15,11 +15,15 @@
  */
 package org.onosproject.provider.lldp.impl;
 
-import com.google.common.collect.ArrayListMultimap;
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableMap;
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.Lists;
+import java.nio.ByteBuffer;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -66,14 +70,12 @@
 import org.onosproject.net.provider.ProviderId;
 import org.onosproject.provider.lldpcommon.LinkDiscovery;
 
-import java.nio.ByteBuffer;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
-import java.util.concurrent.CompletableFuture;
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Lists;
+import com.google.common.util.concurrent.MoreExecutors;
 
 import static org.easymock.EasyMock.createMock;
 import static org.easymock.EasyMock.expect;
@@ -146,6 +148,8 @@
 
         provider.activate(null);
 
+        provider.eventExecutor = MoreExecutors.newDirectExecutorService();
+
         providerService = linkRegistry.registeredProvider();
     }