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

@@ -125,13 +125,10 @@ XLogReaderFree(XLogReaderState *state)
 	int			block_id;
 
 	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->main_data)
 		pfree(state->main_data);