Don't treat no-cache as no-store

[PSUdaemon]

https://httpwg.github.io/specs/rfc7234.html#rfc.section.5.2.2.2

no-cache in a response means you can still store on your proxy, you just cannot serve it without revalidation. We should store the content but immediately expired. Then revalidate it upon request.

I can work on a patch for this if you would like.

[lox]

Ah yup, I think I have a branch somewhere that addressed this, but I can't find it. PR's welcome.