Moved update of DNA plugin among update plugins
    
    To make the code more general, moved the update_dna_shared_config
    among other update plugins.
    
    Bugfix: DNA shared config connection protocol was compared to a
    method string which would result in a try to always update it
    even if there was no need to.
    
    https://fedorahosted.org/389/ticket/48373 causes that two
    shared DNA config entries are created instead of one.
    
    https://fedorahosted.org/freeipa/ticket/6392
    
    Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>