Docker build instructions do not work

Followed instructions here https://github.com/linkedin/iris/tree/master/ops/packer

```
packer build -only=docker ./output/iris.json

docker: mv: cannot stat '/home/iris/source/ops/config/systemd/uwsgi-iris.service': No such file or directory
==> docker: Killing the container: 3ae3090eb6e4e524f7d3e71decf92642267086b7b28aebcc2e23baad6115eb85
Build 'docker' errored: Script exited with non-zero exit status: 1

==> Some builds didn't complete successfully and had errors:
--> docker: Script exited with non-zero exit status: 1

==> Builds finished but no artifacts were created.

```

Start in ops/packer and run the documented `packer build -only=docker ./output/iris.json` command. Trace why the build cannot find `ops/config/systemd/uwsgi-iris.service`; done means the Docker build completes successfully and creates an artifact.

Written by the indexing model from the issue text.