Sometimes when DHCPv6 client is started in stateless mode (i.e. with '-6 -S' command line options) on network interface which is not fully "up".
dhclient fails to run, because network interface does not have link-local address yet, which is needed for DHCPv6 client.
A wait loop was added into dhclient-script.
dhclient doesn't fail due to missing link-local address.