Fix test-stem `test_take_ownership_via_controller` failure
Stem's test_take_ownership_via_controller test fails when run in Travis CI. This is a recent failure, some time in the last month or two.
See, for example: https://travis-ci.org/torproject/tor/jobs/639546796
We're trying to work out if it's a Tor or Stem issue right now, here's the corresponding Stem ticket: https://github.com/torproject/stem/issues/52
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information