[ONOS-5560] IntentCleanupTestMock::corruptPoll fails very rarely due to race

Change-Id: I24fa09b2c6cfd2a9f95fd8fccc168bcc25b01c78
diff --git a/core/net/src/test/java/org/onosproject/net/intent/impl/IntentCleanupTestMock.java b/core/net/src/test/java/org/onosproject/net/intent/impl/IntentCleanupTestMock.java
index 9d29729..d5d2af0 100644
--- a/core/net/src/test/java/org/onosproject/net/intent/impl/IntentCleanupTestMock.java
+++ b/core/net/src/test/java/org/onosproject/net/intent/impl/IntentCleanupTestMock.java
@@ -116,7 +116,9 @@
         expectLastCall().once();
         replay(service);
 
-        cleanup.run(); //FIXME broken?
+        synchronized (service) {
+            cleanup.run(); //FIXME broken?
+        }
         verify(service);
         reset(service);
     }