Added time to error message when port open timed out.

Author: AlexeyKuznetsov-DD

dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/utils/PortUtils.java

@@ -105,7 +105,8 @@ private static boolean isPortOpen(String host, int port) {
 
   public static void waitForPortToOpen(
       final int port, final long timeout, final TimeUnit unit, final Process process) {
-    final long waitUntil = System.currentTimeMillis() + unit.toMillis(timeout);
+    final long startedAt = System.currentTimeMillis();
+    final long waitUntil = startedAt + unit.toMillis(timeout);
 
     while (System.currentTimeMillis() < waitUntil) {
       try {
@@ -133,7 +134,13 @@ public static void waitForPortToOpen(
       }
     }
 
-    throw new RuntimeException("Timed out waiting for port " + port + " to be opened");
+    throw new RuntimeException(
+        "Timed out waiting for port "
+            + port
+            + " to be opened, started to wait at: "
+            + startedAt
+            + ", timed out at: "
+            + System.currentTimeMillis());
   }
 
   public static void waitForPortToOpen(String host, int port, long timeout, TimeUnit unit) {