selftests: netdevsim: fix the udp_tunnel_nic test

This test is missing a whole bunch of checks for interface
renaming and one ifup. Presumably it was only used on a system
with renaming disabled and NetworkManager running.

Fixes: 91f430b2 ("selftests: net: add a test for UDP tunnel info infra")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240123060529.1033912-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>