selftests/bpf: Handle forwarding of UDP CLOCK_TAI packets

With changes in the design to forward CLOCK_TAI in the skbuff
framework,  existing selftest framework needs modification
to handle forwarding of UDP packets with CLOCK_TAI as clockid.

Signed-off-by: Abhishek Chauhan <quic_abchauha@quicinc.com>
Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20240509211834.3235191-4-quic_abchauha@quicinc.com


Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>