On some Merlin routers, due to ntp bug, after rebooing, dnsmasq config
was restored to default without ctrld changes, causing ctrld stop
working. Workaround this problem by catching restart diskmon event,
which is triggered by ntpd_synced, then restart dnsmasq.
This commit add the ability for ctrld to gather client information,
including mac/ip/hostname, and send to Control-D server through a
config per upstream.
- Add send_client_info upstream config.
- Read/Watch dnsmasq leases files on supported platforms.
- Add corresponding client info to DoH query header
All of these only apply for Control-D upstream, though.