Load GeoIP[v6]File from the build directory when testing a tor build in chutney

We should test that our build's GeoIP[v6]Files parse by loading them in chutney networks.

Currently, chutney loads the files from /usr, which is good if the running tor is in /usr, but useless for builds.

Here's one way to make this work:

1. Set an environmental variable and test-network.sh argument for each GeoIP[v6]File
2. Substitute those env vars into chutney's torrc_templates/common.i