Cached requests to /simple/* should be indicated in pip install -v

[Julian]

A request within the 10 minute cache window for packages that are being pip install-ed shows (snipped) Getting page https://pypi.python.org/simple/faf/ for instance, but that's a bit of a lie, the page wasn't loaded, and its contents may differ and cause pip to do different things than what it actually decides to do.

This makes debugging difficult unless you actually know there's an additional cache involved (I assumed it was Fastly's fault).

[dstufft]

Closing this as a duplicate of #2905 as that is a more general issue.