Unless an explicit fallback is configured. Untested.

Includes a merge of radiod and redirectord, updates to more modern Go
idioms, adoption of the higher level etcd concurrency primitives, and
a lot of other minor implementation changes.

The refactor is still incomplete: the daemons won't compile and the
code to start the RPC servers is missing.

This will limit useless reloads (and related killSources), for instance
when transcoding parameters change. Also, improve the icecast
config generation test.

Adds a new metric to NodeStatus (MaxListeners) so that it is available
to the traffic control logic.

This allows running the service on a single port: with the
--enable-icecast-proxy option, all requests can go through
redirectord.