[Merge] ~callmepk/livecd-rootfs/+git/livecd-rootfs:ubuntu/focal into livecd-rootfs:ubuntu/focal

[Patrick Wu]

Thanks for the information. Here is the reasoning:

- use of linux-azure, which is the optimized kernel for Hyper-V suggested by Microsoft
- xRDP configuration changes due to the config changes in this version compared to 18.04.
- 46-allow-update-repo.pkla inclusion to aviod "Authentication required to refresh system repositories" bug in xRDP

I also include them in the commit message.
-- 
https://code.launchpad.net/~callmepk/livecd-rootfs/+git/livecd-rootfs/+merge/387300
Your team Ubuntu Core Development Team is requested to review the proposed merge of ~callmepk/livecd-rootfs/+git/livecd-rootfs:ubuntu/focal into livecd-rootfs:ubuntu/focal.