* Ensure the mDNS mode is set every time network state changes
Eliminates (mostly) duplicate code
* Add custom NTP and HTTP time sync servers
Since the ordering may have been previously defaulted and saved as "ntp,http", but that was being ignored and fallback-defaults were being used, in Ordering, `ntp` means use the fallback NTP servers, and `http` means use the fallback HTTP URLs. Thus `ntp_user_provided` and `http_user_provided` are the user specified static lists.
* Add support for using DHCP-provided NTP server