fix(*): all services ensure valid config file on reload

Closes #1099
Replaces #1626
test(builder): update etcd keys in builder test

The confd templates expected some more etcd keys than were seeded
before. Add those extra keys in.
fix(router): add check command for nginx config

Check for `<no value>` in nginx config, which usually means that
something is wrong with the configuration in etcd.
Merge pull request #1629 from deis/fix/check-config

fix(*): all services ensure valid config file on reload
fix(tests): take a nap after fleet restart
feat(*): add `make test-style` targets

This gives us an opporunity to run code checkers and linters as part
of testing, as we used to on travis-ci.org. By default, unit tests
will check code syntax and style first.
ref(*): clean up Go and Python code for `make test-style`