Silence non-critical messages from Jetty in tests

This makes the log output much more readable.

Change-Id: I318900cc250d77faacb90a8dcc84f3bdb525ac1b
Signed-off-by: Edwin Kempin <ekempin@google.com>
diff --git a/java/com/google/gerrit/acceptance/GerritServer.java b/java/com/google/gerrit/acceptance/GerritServer.java
index 981ee6b..96a9053 100644
--- a/java/com/google/gerrit/acceptance/GerritServer.java
+++ b/java/com/google/gerrit/acceptance/GerritServer.java
@@ -228,6 +228,9 @@
 
           // Silence non-critical messages from apache.http.
           .put("org.apache.http", Level.WARN)
+
+          // Silence non-critical messages from Jetty.
+          .put("org.eclipse.jetty", Level.WARN)
           .build();
 
   private static boolean forceLocalDisk() {