fix_snmp set no community at all and opened the management zone's
udp/161 to every source, with a rule named after an application; a
second fix_snmp in the system mixin was shadowed and never ran (#5).
install_lldpd, install_auc and install_coreutils_base64 were actions of
their own.
The driver implements napalm-device-types 4.13's templates instead:
- configure_snmp_agent(settings): snmpd installed when missing;
community, contact and location in UCI with one com2sec (com2sec6)
per allowed source; the zone-resolving firewall step of the old fix,
now limited to the sources (src_ip) and named Allow-SNMP; snmpd
enabled, restarted and listening;
- get_management_peer() from SSH_CONNECTION;
- ensure_package(name) from the base package, over install_package.
A community, contact or location that would break UCI is refused.
BREAKING CHANGE: run_device_action is removed. Requires
napalm-device-types 4.13.
Closes#5. Part of #13.
