Allow diagnostics to be downloaded on port 62374

A client like `pinata diagnose` can do the equivalent of:

  nc 192.168.64.2 62374 > foo.tar

and find `foo.tar` contains

- the output of `/usr/bin/diagnostics`
- `iptables -L`
- `netstat -an`
- `ps uax`
- `docker ps`
- `dig docker.com`
- `wget http://docker.com`

This will allow us to diagnose various in-VM faults, without having
to ask the user to access the console and run commands.

Signed-off-by: David Scott <dave.scott@docker.com>

alpine/Dockerfile

@@ -34,6 +34,8 @@ COPY packages/docker/docker /usr/bin/
 COPY packages/docker/etc /etc/
 COPY packages/docker-x/docker-x /usr/bin/
 COPY packages/diagnostics/diagnostics /usr/bin/
+COPY packages/diagnostics/diagnostics-server /usr/bin/
+COPY packages/diagnostics/diagnostics-download /usr/bin/
 COPY packages/diagnostics/etc /etc/
 COPY packages/automount/etc /etc/
 COPY packages/9pinit/etc /etc/