Rebase hardware pollsters to use new inspector interface

Change all the hardware pollsters to use new inspector interface
inspect_generic(), and remove the old interfaces.

Partial implements: blueprint snmp-improvement.
Partial-Bug: 1286132

Change-Id: Icc566ec8c4dbe1c0883c7e0d653480c5659f30b9
Merge "Rebase hardware pollsters to use new inspector interface"