move unit test docker up to gcc10

The project will soon be moving to gcc10 so ensure we're running it in
CI. Getting to gcc10 required an update to the latest Ubuntu LTS
release. The latest Ubuntu release moved to python 3.8.

Change-Id: I555c446bc9f9ec4b12e6ed270f5689d75586a4e7
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
2 files changed