R=kevmoo@google.com

Review URL: https://codereview.chromium.org//2046563003 .

This reverts back to 20ddf7ce.

The intermediate commits were meant to go to a development branch.

We used to be storing packages from HTTP hosted sources in directories
named after the hostname. There was no distinction between a package
from an HTTP source and an HTTPS source with the same name. This was
contrary to the rest of pub's logic, which considered those different
sources.

Closes #1418

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//2028853002 .