Cherry-pick request (LaunchPad bug #1860986)

[Maxime Leroy]

Hello,

I have done some tests with ovs + vxlan with a DOCKER environnement.
The issue is the following one: Packets encapsulated into a vxlan
tunnel with openvswitch don't have the same udp source port for the
first packet and the following ones of the same TCP flow.

I've described the issue in detail in this LaunchPad bug:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1860986

This has been fixed in v5.5 by the following upstream commit:
* https://github.com/torvalds/linux/commit/bd1903b7c4596

To fix this issue, some patches need to be also back-ported on
openvswitch too. See the following bug:
https://bugs.launchpad.net/ubuntu/+source/openvswitch/+bug/1860987

Best Regards.

Thanks,

Maxime