Add an ugly workaround for FEDORA-2023-f6afa6f9e5 rebase issue
    
    There's a weird issue with the rpmostree_rebase test for this
    update:
    https://bodhi.fedoraproject.org/updates/FEDORA-2023-f6afa6f9e5#comment-2919613
    it doesn't reproduce locally (I can type fine after doing the
    same things the test does up to the rollback) and I can't think
    of any possible cause, and I don't want to hold the update up.
    So we're just gonna work around it and hope this doesn't start
    happening to all F38 update tests after this goes stable. If it
    does, we'll have to do the workaround for all of them.
    
    The workaround is just to rollback and reboot 'blindly', instead
    of checking the rollback command works. The drawback is that if
    the rollback command fails we'll wait 7.5 minutes before giving
    up on it, and it'll be a bit less clear exactly what happened.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>