IPMI: allow searching sensors by full name as well as id

Some BMC cards provide multiple sensors belonging to different entities but with the same ID. Only full name differs for these sensors. A good example is Dell iDRAC 6 card. Zabbix sensor debug output looks like the following:

7395:20180213:131244.993 Added sensor: host:'10.0.4.74:623' id_type:0 id_sz:5 id:'Temp' reading_type:0x1 ('threshold') type:0x1 ('temperature') full_name:'1(10.1).Temp'
7395:20180213:131244.994 Added sensor: host:'10.0.4.74:623' id_type:0 id_sz:5 id:'Temp' reading_type:0x1 ('threshold') type:0x1 ('temperature') full_name:'1(3.2).Temp'
7395:20180213:131244.995 Added sensor: host:'10.0.4.74:623' id_type:0 id_sz:5 id:'Temp' reading_type:0x1 ('threshold') type:0x1 ('temperature') full_name:'1(3.1).Temp'

Here you can see three 'Temp' readings which cannot be distinguished one from other easily.

Proposed and included patch stores sensors full name in the sensors list and adds a search function that finds sensor by full name, allowing to use full_name field values as IPMI sensor IDs.