selftests/net: l2_tos_ttl_inherit.sh: Set IPv6 addresses with "nodad".

selftests/net: l2_tos_ttl_inherit.sh: Set IPv6 addresses with "nodad".

[ Upstream commit e59370b2e96eb8e7e057a2a16e999ff385a3f2fb ]

The ping command can run before DAD completes. In that case, ping may
fail and break the selftest.

We don't need DAD here since we're working on isolated device pairs.

Fixes: b690842d12fd ("selftests/net: test l2 tunnel TOS/TTL inheriting")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>