apt-get scenarios are fragile

These tests could use some retrying with new tor circuits.

    [sudo] password for amnesia: W: GPG error: tor+http://ftp.us.debian.org wheezy-backports Release: The following signatures were invalid: BADSIG 8B48AD6246925553 Debian Archive Automatic Signing Key (7.0/wheezy) <ftpmaster@debian.org>
    W: Failed to fetch tor+http://ftp.us.debian.org/debian/dists/testing/main/binary-i386/Packages  Hash Sum mismatch
    W: Failed to fetch tor+http://ftp.us.debian.org/debian/dists/testing/non-free/binary-i386/Packages  Hash Sum mismatch
    W: Failed to fetch tor+http://ftp.us.debian.org/debian/dists/testing/main/i18n/Translation-en  404  Not Found
    W: Failed to fetch tor+http://ftp.us.debian.org/debian/dists/wheezy-backports/contrib/binary-i386/Packages  404  Not Found
    E: Some index files failed to download. They have been ignored, or old ones used instead.

Of course, retrying doesn’t won’t guarantee that the test can succeed. The forthcoming freezable-apt repo OTOH combined with retrying might.

Feature Branch: test/10496-apt-get-scenarios-are-fragile

Parent Task: #10288

Original created by @kytv on 10496 (Redmine)