GEODE-6662 NioPlainEngine.ensureWrappedCapacity

Fixing a memory leak:

Return the old buffer to the Buffers pool after copying its
contents to a newly allocated buffer.

(cherry picked from commit 064892c)

Author: bschuchardt

geode-core/src/main/java/org/apache/geode/internal/net/NioPlainEngine.java

@@ -76,6 +76,7 @@ public ByteBuffer ensureWrappedCapacity(int amount, ByteBuffer wrappedBuffer,
       buffer = Buffers.acquireBuffer(bufferType, amount, stats);
       buffer.clear();
       buffer.put(oldBuffer);
+      Buffers.releaseBuffer(bufferType, oldBuffer, stats);
       lastReadPosition = buffer.position();
       lastProcessedPosition = 0;
     }

geode-core/src/test/java/org/apache/geode/internal/net/NioPlainEngineTest.java

@@ -58,12 +58,14 @@ public void unwrap() {
 
   @Test
   public void ensureWrappedCapacity() {
-    ByteBuffer wrappedBuffer = ByteBuffer.allocate(100);
+    ByteBuffer wrappedBuffer = Buffers.acquireReceiveBuffer(100, mockStats);
+    verify(mockStats, times(1)).incReceiverBufferSize(any(Integer.class), any(Boolean.class));
     wrappedBuffer.put(new byte[] {0, 1, 2, 3, 4, 5, 6, 7, 8, 9});
     nioEngine.lastReadPosition = 10;
     int requestedCapacity = 210;
     ByteBuffer result = nioEngine.ensureWrappedCapacity(requestedCapacity, wrappedBuffer,
-        Buffers.BufferType.UNTRACKED, mockStats);
+        Buffers.BufferType.TRACKED_RECEIVER, mockStats);
+    verify(mockStats, times(2)).incReceiverBufferSize(any(Integer.class), any(Boolean.class));
     assertThat(result.capacity()).isGreaterThanOrEqualTo(requestedCapacity);
     assertThat(result).isNotSameAs(wrappedBuffer);
     // make sure that data was transferred to the new buffer