[#2573] UnpooledUnsafeDirectByteBuf.setBytes(int,ByteBuf,int,int) fails to use fast-path when src has array

Motivation:

UnpooledUnsafeDirectByteBuf.setBytes(int,ByteBuf,int,int) fails to use fast-path when src uses an array as backing storage. This is because the if else uses the wrong ByteBuf for its check.

Modifications:

- Use correct ByteBuf when check for array as backing storage
- Also eliminate unecessary check in UnpooledDirectByteBuf which always fails anyway

Result:

Faster setBytes(...) when src ByteBuf is backed by an array.

No more IndexOutOfBoundsException or data-corruption.

buffer/src/main/java/io/netty/buffer/UnpooledDirectByteBuf.java

@@ -411,9 +411,7 @@ public class UnpooledDirectByteBuf extends AbstractReferenceCountedByteBuf {
     @Override
     public ByteBuf setBytes(int index, ByteBuf src, int srcIndex, int length) {
         checkSrcIndex(index, length, srcIndex, src.capacity());
-        if (buffer.hasArray()) {
-            src.getBytes(srcIndex, buffer.array(), index + buffer.arrayOffset(), length);
-        } else if (src.nioBufferCount() > 0) {
+        if (src.nioBufferCount() > 0) {
             for (ByteBuffer bb: src.nioBuffers(srcIndex, length)) {
                 int bbLen = bb.remaining();
                 setBytes(index, bb);

buffer/src/main/java/io/netty/buffer/UnpooledUnsafeDirectByteBuf.java

@@ -355,7 +355,7 @@ public class UnpooledUnsafeDirectByteBuf extends AbstractReferenceCountedByteBuf
         if (length != 0) {
             if (src.hasMemoryAddress()) {
                 PlatformDependent.copyMemory(src.memoryAddress() + srcIndex, addr(index), length);
-            } else if (buffer.hasArray()) {
+            } else if (src.hasArray()) {
                 PlatformDependent.copyMemory(src.array(), src.arrayOffset() + srcIndex, addr(index), length);
             } else {
                 src.getBytes(srcIndex, this, index, length);