fix parsing file io for MySQL 5.5

In MySQL 5.5 the innodb status shows additionally aio reads and aio writes for
each thread in square brackets.

plugins/node.d/mysql_.in

@@ -1187,7 +1187,7 @@ sub parse_transactions {
 sub parse_file_io {
     parse_section(
 	sub {
-	    m/\GPending normal aio reads: (\d+), aio writes: (\d+),\n\s*ibuf aio reads: (\d+), log i\/o's: (\d+), sync i\/o's: (\d+)\n/gc && do {
+	    m/\GPending normal aio reads: (\d+)(?: \[(?:\d+, )*\d+\] )?, aio writes: (\d+)(?: \[(?:\d+, )*\d+\] )?,\n\s*ibuf aio reads: (\d+), log i\/o's: (\d+), sync i\/o's: (\d+)\n/gc && do {
 		$data->{ib_iop_aioread}  = $1;
 		$data->{ib_iop_aiowrite} = $2;
 		$data->{ib_iop_ibuf_aio} = $3;