provision: Replace --production-travis with --build-release-tarball-only.
provision: Replace --production-travis with --build-release-tarball-only.

--production-travis was renamed to --build-release-tarball-only, both
  in master and in the 2.1.5 release.

Fixes #256.

Galexrt/docker-zulip,Galexrt/docker-zulip,Galexrt/docker-zulip