The current approach to get default route IP is finding the LAN
interface with the same MAC address. However, there could be multiple
interfaces like that, making ctrld confused.
This commit fixes this issue, by listing all possible private IPs, then
sorting them and use the smallest one for router self queries.
For reporting router queries, ctrld uses private IP of the default route
interface. However, when the default route is conntected directly to
ISP, the interface will have a public IP, and another interface with the
same MAC address will be created for LAN ip. So when no private IP found
for default route interface, ctrld must look at the other interface to
find the corret LAN ip.
The only reason that forces ctrld to depend on vyatta-dhcpd service on
EdgeOS is allowing ctrld to watch lease files properly, because those
files may not be created at the time client info table initialized.
However, on some EdgeOS version, vyatta-dhcpd could not start with an
empty config file, causing restart loop itself, flooding systemd log,
making the router run out of memory.
To fix this, instead of depending on vyatta-dhcpd, we should just watch
for lease files creation, then adding them to watch list.
While at it, also making ctrld starts after nss-lookup, ensuring we have
a working DNS before starting ctrld.
Using the same approach as in cd mode, but do it only once when running
ctrld the first time, then the config will be re-used then.
While at it, also adding Dockerfile.debug for better troubleshooting
with alpine base image.
