Made the tag counter a non-static variable.

This was needed to avoid random test failures where a test running
before another could increase the tag and fail the test.

jetty-io/src/main/java/org/eclipse/jetty/io/MappedByteBufferPool.java

@@ -120,15 +120,15 @@ public class MappedByteBufferPool implements ByteBufferPool
         return direct ? directBuffers : heapBuffers;
     }
 
-    private static AtomicInteger __tag = new AtomicInteger();
-    
     public static class Tagged extends MappedByteBufferPool
     {
+        private final AtomicInteger tag = new AtomicInteger();
+
         public ByteBuffer createIndirect(int capacity)
         {
-            ByteBuffer buffer =  BufferUtil.allocate(capacity+4);
+            ByteBuffer buffer = BufferUtil.allocate(capacity + 4);
             buffer.limit(4);
-            buffer.putInt(0,__tag.incrementAndGet());
+            buffer.putInt(0, tag.incrementAndGet());
             buffer.position(4);
             buffer.limit(buffer.capacity());
             ByteBuffer slice = buffer.slice();