increasing latch timeout, which sometimes fails

Change-Id: Idad05c82f86cbe0024206db2ea6699e4fe06bfa4
diff --git a/utils/nio/src/test/java/org/onlab/nio/AbstractLoopTest.java b/utils/nio/src/test/java/org/onlab/nio/AbstractLoopTest.java
index 91fc0d7..094a093 100644
--- a/utils/nio/src/test/java/org/onlab/nio/AbstractLoopTest.java
+++ b/utils/nio/src/test/java/org/onlab/nio/AbstractLoopTest.java
@@ -15,7 +15,7 @@
  */
 public abstract class AbstractLoopTest {
 
-    protected static final long MAX_MS_WAIT = 500;
+    protected static final long MAX_MS_WAIT = 1500;
 
     /** Block on specified countdown latch. Return when countdown reaches
      * zero, or fail the test if the {@value #MAX_MS_WAIT} ms timeout expires.