Add glib-networking to multilib whitelist
    
    Make sure glib-networking is always installed multilib. Right now the
    dependency that makes glib-networking multilib is Requires:
    glib-networking%{_isa} in libsoup, but if libsoup is not in the same
    repo as glib-networking (as is the case right now with the F30 updates
    repo), glib-networking can drop out of multilib.
    
    Fix this by explicitly listing it as multilib.
    
    https://pagure.io/releng/issue/8365
    
    Signed-off-by: Kalev Lember <klember@redhat.com>