delay dhcp'ing on he vpn until openvpn had time to configure the interface

wtf:

Jul  8 15:08:15 hetz3 ovpn-dasz-bridge[24655]: Note: Cannot ioctl TUNSETIFF tap0: Device or resource busy (errno=16)
Jul  8 15:08:15 hetz3 ovpn-dasz-bridge[24655]: Assertion failed at misc.c:222
Jul  8 15:08:15 hetz3 ovpn-dasz-bridge[24655]: Exiting