minion: Allow retrieval of GitHub keys
minion: Allow retrieval of GitHub keys

Before, retrieving GitHub keys would error on the minion because the
Alpine container didn't contain some certificates. This patch makes the
minion use the host's certificates.

kayousterhout/quilt,tejasmanohar/quilt,NetSys/quilt,quilt/quilt,ejj/quilt-dev,secant/quilt,PenguinToast/quilt,kklin/kelda,secant/quilt,stevenlin598/quilt,kklin/quilt,secant/quilt,ejj/quilt-dev,mmussomele/quilt,stevenlin598/quilt,quilt/quilt,kelda/kelda,tejasmanohar/quilt,mmussomele/quilt,LuiseV/quilt,secant/quilt,PenguinToast/quilt,mmussomele/quilt,kklin/quilt,kklin/kelda,mmussomele/quilt,LuiseV/quilt,mmussomele/quilt,tejasmanohar/quilt,mmussomele/quilt,tejasmanohar/quilt,quilt/quilt,kelda/kelda,PenguinToast/quilt,NetSys/quilt,PenguinToast/quilt,ejj/quilt-dev,kayousterhout/quilt,stevenlin598/quilt,stevenlin598/quilt,kklin/kelda,kayousterhout/quilt,kelda/kelda,PenguinToast/quilt,LuiseV/quilt,kelda/kelda,NetSys/quilt,NetSys/quilt,quilt/quilt,ejj/quilt-dev,LuiseV/quilt,kklin/quilt,stevenlin598/quilt,secant/quilt,kayousterhout/quilt,NetSys/quilt,LuiseV/quilt,kklin/kelda,stevenlin598/quilt,kklin/quilt