machines bugfixes

machines bugfixes

- handle interface:deleted and host:deleted events
- coredns plugin: only call tryInit if we fail to load the saved state from disk
- coredns plugin: make all hostname lookups case insensitive
- coredns plugin: fix <interface>.<host>.<domain> lookups
- coredns plugin: bump init ticker interval to 10 seconds
- coredns plugin: tighten lock window when updating registry from API
- coredns plugin: increase verbosity level of some really noisy log messages
- tweak mqtt startup
- fix `allow/deny unknown-clients` being added to dhcp subnets with only one range
- add captive portal service in openbsd, fix maclist template