minion: Wait for self to exist before syncing keys
minion: Wait for self to exist before syncing keys

Before, there was a cosmetic race condition where we would try to get
the self minion before it was created, and an error would be logged.
This patch makes us wait until a minion exists before attempting to sync
SSH keys.

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