remove the dependency of rpmUtils
    
    The rpmUtils module is provided yum-utils package, which is only
    available for Python 2. There is no replacement for the functionality in
    DNF.
    
    There is a proposal to add this functionality to rpm itself, but it's
    not really moving forward very much:
    https://bugzilla.redhat.com/show_bug.cgi?id=1072972
    
    As a short term solution let's copy the needed parts of rpmUtils.arch
    module directly to pungi code base.
    
    Fixes: https://pagure.io/pungi/issue/533
    Signed-off-by: Qixiang Wan <qwan@redhat.com>