sg "docker" check doesn't seem to work

Created by: chrismwendt

sg seems to think Docker is running, but then minio fails because it's not:

$ sg start enterprise-codeintel
✅ Check "docker" success!
...
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Failed to build minio: 'bash -c mkdir -p $MINIO_LOGS
mkdir -p $MINIO_DISK
CACHE=true ./docker-images/minio/build.sh >$MINIO_LOG_FILE 2>&1' failed: : exit status 1
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$ cat $HOME/.sourcegraph-dev/logs/minio/minio.log
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?