Fix memory leak in xlogreader facility.

XLogReaderFree failed to free the per-block data buffers, when they
happened to not be used by the latest read WAL record.

Michael Paquier. Backpatch to 9.5, where the per-block buffers were added.

src/backend/access/transam/xlogreader.c

@@ -126,11 +126,8 @@ XLogReaderFree(XLogReaderState *state)
 
 	for (block_id = 0; block_id <= state->max_block_id; block_id++)
 	{
-		if (state->blocks[block_id].in_use)
-		{
-			if (state->blocks[block_id].data)
-				pfree(state->blocks[block_id].data);
-		}
+		if (state->blocks[block_id].data)
+			pfree(state->blocks[block_id].data);
 	}
 	if (state->main_data)
 		pfree(state->main_data);