Fix vector raw inintialization logic

Vector RAW in UML needs to BPF filter its own MAC only
if QDISC_BYPASS has failed. If QDISC_BYPASS is successful, the
frames originated locally are not visible to readers on the
raw socket.

Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>