fix(docker): Clean up files left from running tests
fix(docker): Clean up files left from running tests

When running the end-to-end tests, LevelDB (via pbf2json) leaves behind
its data in /tmp, and does not clean itself up.

Future containers run using this image will almost certainly also run
`pbf2json`, and may not run using the same user id, meaning permissions
to overwrite the files in `/tmp` may not exist. Thus, it's best if they
are removed in the Docker image.

Connects https://github.com/pelias/pelias/issues/745
Connects https://github.com/pelias/docker/pull/20

pelias/openstreetmap,pelias/openstreetmap