Always follow redirects in network jobs (#4905)

Always follow redirects in network jobs (#4905)

This is a move away from the original policy where jobs
would only follow redirects in special cases.

Two restrictions are in place:

1. We do not allow protocol downgrades (https -> http)
2. We stop redirects after we find them looping (e.g. old = new url, or
indirectly when looping 10 times).

This is closer to RFC conforming behavior, although currently
we will treat 301 replies like they were 302. This is for a separate
commit.

Error handling (and display) also needs improvement.

Addresses #2791