Whenever the snmp plugin was configured with a table with automatic field
discovery, if one of those fields was explicitly overridden in the config and
the value of is_tag was changed, the field would be duplicated, once as a tag
& once as a field.
This change fixes the behavior so that if a field is explicitly configured,
automatic table field discovery doesn't touch it.
Also consolidated the translation code to obtain all info with just 1 command execution.
Also split test command mocks out to their own file for cleanliness.
Sebastian Spaink
reimda
Mya
Tuamas
Patrick Hemmer
Patrick Hemmer