I noticed in the static deltas tests, there were some tests that
should have been under `-o pipefail` to ensure we properly propagate
errors.
There were a few places where we were referencing undefined variables.
Overall, this is clearly a good idea IMO.
Eliminates the need for constantly passing --sysroot=sysroot, but
also makes ostree place remote configs for sysroot/ostree/repo in
sysroot/etc/ostree/remotes.d where they should have been all along.
We don't want to allow MITM attackers to intercept upgrade requests
and provide clients with older OS versions vulnerable to security
flaws.
Only "ostree admin upgrade" gets this behavior for now - whether we
want to do it for "ostree admin switch" is another question.