fix_snmp wrote an application's snmpd.conf (community public, Managed
by netOrk, netork@localhost) and judged itself by a local snmpget.
The drivers implement napalm-device-types 4.13's SnmpAgentMixin steps
instead: net-snmp installed, snmpd.conf with one rocommunity line per
allowed source (staged without privilege, installed by root), snmpd
enabled and restarted. pf and ipfw rules stay the operator's. A
community or text that would break the file is refused. The caller
verifies with its own SNMP client.
Also get_management_peer() from SSH_CONNECTION, ensure_package from
the base package, and get_snmp_config no longer assumes "public".
BREAKING CHANGE: run_device_action is removed. Requires
napalm-device-types 4.13.
Part of #12 (the OpenBSD new_version text is still open).
Christian Manivong