Updates to the snmp-power-driver spec
Updates to the snmp-power-driver spec

This commit improves the SNMP terminology to make it
better aligned with the language conventionally being
used now days.

Also pysnmp-related facts updated to reflect current
features and capabilities of the package.

Change-Id: I9ab80c7bb46e0c837904d8bb19f5ef4c7a0034e6

openstack/ironic-specs