still seeing flakyness.  Increase retries.

Change-Id: I988afa2922dc503bcdff455822088ad22c854d97
diff --git a/tests/tests/net/src/android/net/cts/ListeningPortsTest.java b/tests/tests/net/src/android/net/cts/ListeningPortsTest.java
index 0a32bd7..b6e6efb 100644
--- a/tests/tests/net/src/android/net/cts/ListeningPortsTest.java
+++ b/tests/tests/net/src/android/net/cts/ListeningPortsTest.java
@@ -67,7 +67,7 @@
         assertNoListeningUdpPorts("/proc/net/udp6");
     }
 
-    private static final int RETRIES_MAX = 4;
+    private static final int RETRIES_MAX = 6;
 
     /**
      * UDP tests can be flaky due to DNS lookups.  Compensate.