GH-238: Stop TestNettyAllocator wrapping Netty's empty buffer in a 1024-byte ArrowBuf

TestNettyAllocator.testMemoryUsage wrapped a 1024-byte NO_OP ArrowBuf around
the memory address of PooledByteBufAllocatorL's empty buffer, whose native
allocation is only a few bytes. The test only reads the address today, but
any read or write through that buffer would run past the end of the native
allocation, as in TestEmptyArrowBuf (#1426).

The buffer isn't needed: the memory usage log the test waits for comes from
the status thread that the PooledByteBufAllocatorL constructor starts when
TRACE logging is enabled. Construct the allocator directly instead.

Closes #238.

Author: jbonofre

memory/memory-netty/src/test/java/org/apache/arrow/memory/netty/TestNettyAllocator.java

@@ -25,8 +25,6 @@
 import io.netty.buffer.PooledByteBufAllocatorL;
 import java.util.Collections;
 import java.util.stream.Collectors;
-import org.apache.arrow.memory.ArrowBuf;
-import org.apache.arrow.memory.ReferenceManager;
 import org.junit.jupiter.api.Test;
 import org.slf4j.LoggerFactory;
 
@@ -43,14 +41,8 @@ public void testMemoryUsage() {
       logger.setLevel(Level.TRACE);
       logger.addAppender(memoryLogsAppender);
       memoryLogsAppender.start();
-      try (ArrowBuf buf =
-          new ArrowBuf(
-              ReferenceManager.NO_OP,
-              null,
-              1024,
-              new PooledByteBufAllocatorL().empty.memoryAddress())) {
-        buf.memoryAddress();
-      }
+      // Creating the allocator with TRACE logging enabled starts the thread that logs memory usage.
+      new PooledByteBufAllocatorL();
       boolean result = false;
       long startTime = System.currentTimeMillis();
       while ((System.currentTimeMillis() - startTime)