chore(builder): remove unused authorized_keys

The authorized_keys file that is actually in use is at
builder/templates/authorized_keys. This file does nothing.
fix(controller): change api logs response to 204 when no logs

The controller previously responded with a 404 (Not Found) when there
were no logs available, it now returns a 204 (No Content).

closes #990
Merge pull request #1003 from ecordell/990-fix-log-http-response

fix(controller): controller returns 204 when no logs instead of 404
Merge pull request #1000 from deis/remove-unused-keys

chore(builder): remove unused authorized_keys
refactor(Makefile): enumerate ROUTER_UNITS as a string

Using $foreach over the list of `ROUTER_UNITS` seems cleaner than
shell looping by incrementing a counter. This does require the use
of the Unix `bc` and `seq` utilities, which should be ubiquitous.
fix(Makefile): use fleetctl to filter actual deis-* units

Call `fleetctl` to see which deis-* units are actually loaded, and then
reference only those in the `make stop` and `make uninstall` commands.
This avoids requiring special logic for router(s) except on start.
Requires `awk`, `sed`, and `tr` utilities, which should be ubiquitous.

This also is future-proofing for `fleetctl` 3.x, which returns errors in
many cases where version 2.0 allowed us to be sloppy. Thus the `deis_units`
def is written to accept filters on columns 2 (LOAD) and 4 (SUB) of the
fleetctl output. We will make more use of this when moving to CoreOS 317.0.0.

Closes #991.
fix(Makefile): include router component in `make build` and friends