Add label for tagging, not tied to the fedora-toolbox name
    
    Currently the toolbox script identifies toolbox images and containers
    by checking whether the com.redhat.component label matches
    "fedora-toolbox". However, as per the Fedora Container Guidelines [1],
    the com.redhat.com label should match the Red Hat Bugzilla component
    name where bugs against the image should be reported. This means that
    images derived from the base fedora-toolbox image would likely end up
    overwriting it.
    
    One option would've been to mandate that all toolbox images have the
    "fedora-toolbox-" prefix in their names. However, it's better to avoid
    putting limitations on how images can be named. The "fedora" name
    wouldn't anyway work for images based on other distributions, and not
    all images are going to use the Red Hat bugzilla for tracking bugs.
    
    It's better to use a tag that's uniquely associated with the toolbox
    project, and isn't tied to a particular distribution or bug tracker.
    
    [1] https://fedoraproject.org/wiki/Container:Guidelines