fix(rootfs): use https if port == 443

[bacongobbler]

following the documentation from https://github.com/deis/workflow/blob/master/src/installing-workflow/configuring-object-storage.md#google-cloud-storage-interoperability-mode, if the port number in DEIS_MINIO_SERVICE_PORT == 443, the configured S3_URL will end up as http://storage.googleapis.com:443, which defeats the purpose.

addresses some of the concerns in #75.

[kmala]

79 will make gcs support natively.....so i don't think this PR is necessary