Merge branch 'ioam6-fix-write-to-cloned-skb-s'

Justin Iurman says:

====================
ioam6: fix write to cloned skb's

Make sure the IOAM data insertion is not applied on cloned skb's. As a
consequence, ioam selftests needed a refactoring.
====================

Link: https://lore.kernel.org/r/20240219135255.15429-1-justin.iurman@uliege.be
Signed-off-by: Paolo Abeni <pabeni@redhat.com>