update service_health route for possible . in name

fixes bug when image name may have dotted version tag
are we sure we're cool letting anything/everything through? Also, we don't have to use the :constrains key anymore?

I also just realized this problem is solved differently in API, see: https://github.com/CenturyLinkLabs/panamax-api/blob/master/config/routes.rb#L36, although I think I like the constraints approach better, so maybe we should go update that code on the API side.