Merge branch 'selftests-seg6-make-srv6_end_dt4_l3vpn_test-more-robust'

Andrea Mayer says:

====================
selftests: seg6: make srv6_end_dt4_l3vpn_test more robust

This pachset aims to improve and make more robust the selftests performed to
check whether SRv6 End.DT4 beahvior works as expected under different system
configurations.
Some Linux distributions enable Deduplication Address Detection and Reverse
Path Filtering mechanisms by default which can interfere with SRv6 End.DT4
behavior and cause selftests to fail.

The following patches improve selftests for End.DT4 by taking these two
mechanisms into account. Specifically:
 - patch 1/2: selftests: seg6: disable DAD on IPv6 router cfg for
              srv6_end_dt4_l3vpn_test
 - patch 2/2: selftets: seg6: disable rp_filter by default in
              srv6_end_dt4_l3vpn_test
====================

Link: https://lore.kernel.org/r/20230510111638.12408-1-andrea.mayer@uniroma2.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>