Use local tile server in selenium tests

We are frequently getting dashboard failures resulting from the openstreetmap tile server refusing requests.  I think the tests are triggering too many requests, and the tile server is set up to prevent DOS attacks.  So, I have downloaded the first five zoom levels in a tarball that goes in our test data store.  When building the selenium tests, the tarball will be downloaded and extracted into the deployment directory automatically.  All of the tests will now request tiles locally, rather than through openstreetmaps.  This should hopefully get rid of the nightly test errors that have been popping up the last few weeks.