vxlan: fix tos value before xmit

vxlan: fix tos value before xmit

BugLink: https://bugs.launchpad.net/bugs/1861929
[ Upstream commit 71130f29979c7c7956b040673e6b9d5643003176 ]

Before ip_tunnel_ecn_encap() and udp_tunnel_xmit_skb() we should filter
tos value by RT_TOS() instead of using config tos directly.

vxlan_get_route() would filter the tos to fl4.flowi4_tos but we didn't
return it back, as geneve_get_v4_rt() did. So we have to use RT_TOS()
directly in function ip_tunnel_ecn_encap().

Fixes: 206aaafcd279 ("VXLAN: Use IP Tunnels tunnel ENC encap API")
Fixes: 1400615d64cf ("vxlan: allow setting ipv6 traffic class")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>