Fix chunk_remaining calculation for zlib.

Regression in last commit required zlib to send each chunk as a
separate block, rather than packing multiple chunks per block.

src/bcast/file_bcast.c

@@ -271,7 +271,7 @@ static int32_t _get_block_zlib(struct bcast_parameters *params,
 	}
 
 	if (remaining) {
-		chunk_remaining = MIN(chunk, remaining);
+		chunk_remaining = MIN(block_len, remaining);
 		out_remaining = max_out;
 		strm.next_out = (void *) *buffer;
 		do {