If ctrld setup the interface correctly, the interface DNS is set to
ctrld listener address. At boot time, the ctrld is not up yet, so it
would break the processing Control D config fetching.
Fixing this by waiting for network up before doing the query.
This commit adds config params to enable local DNS response caching and
control its behavior, allow tweaking the cache size, ttl override and
serving stale response.
