t_client.sh: Check for fping/fping6 availability

Check if fping and fping6 is available before running the real tests,
to avoid misleading test failures.

Signed-off-by: David Sommerseth <davids@redhat.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1384535524-6366-1-git-send-email-dazo@users.sourceforge.net>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7981
Signed-off-by: Gert Doering <gert@greenie.muc.de>