Refresh workaround for occasional FreeIPA web UI cert issue
    
    Investigation suggests that the Firefox certificate validation
    failure we sometimes get when loading the FreeIPA web UI in the
    freeipa_webui test module is a race issue in Firefox itself:
    
    https://bugzilla.mozilla.org/show_bug.cgi?id=1530429
    
    refreshing the page seems to work around the problem, so let's
    do that.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>