Silence non-critical messages from JGit in tests

Change-Id: I6e71efb889eea57e6407974a6d5df74a699d7707
diff --git a/java/com/google/gerrit/acceptance/GerritServer.java b/java/com/google/gerrit/acceptance/GerritServer.java
index 8481545..5448f3b 100644
--- a/java/com/google/gerrit/acceptance/GerritServer.java
+++ b/java/com/google/gerrit/acceptance/GerritServer.java
@@ -229,6 +229,10 @@
 
           // Silence non-critical messages from Jetty.
           .put("org.eclipse.jetty", Level.WARN)
+
+          // Silence non-critical messages from JGit.
+          .put("org.eclipse.jgit.transport.PacketLineIn", Level.WARN)
+          .put("org.eclipse.jgit.transport.PacketLineOut", Level.WARN)
           .build();
 
   private static boolean forceLocalDisk() {