modbus with agent2 gives Unsupported item key. in the web interface

Steps to reproduce:

1. Create an item to get modbus items with the key modbus.get[tcp://MB1,1,4,13,1,float,be,1]. The Host inferface is the zabbix-agent2
   
2. Test
   

When we do this on the command line:

zabbix_get -s x.x.x.x -p 10050 -k 'modbus.get[MB1,1,4,342,1,float,be,1]'
9897112340498888499568427957296824320.000000

/usr/sbin/zabbix_agent2 --test "modbus.get[MB1,1,4,342,1,float,be,1]"
modbus.get[MB1,1,4,342,1,float,be,1]          [s|32443848884651631181415748880180445184.000000]