Hit github.com as Travis' infrastructure's DNS seems to be buggy

Author: slandelle

client/src/test/java/org/asynchttpclient/channel/MaxTotalConnectionTest.java

@@ -69,7 +69,7 @@ public void testMaxTotalConnectionsExceedingException() throws IOException {
 
   @Test(groups = "online")
   public void testMaxTotalConnections() throws Exception {
-    String[] urls = new String[]{"https://google.com", "https://gatling.io"};
+    String[] urls = new String[]{"https://google.com", "https://github.com"};
 
     final CountDownLatch latch = new CountDownLatch(2);
     final AtomicReference<Throwable> ex = new AtomicReference<>();