noble-amd64-hafnium: use the python in the venv

Created a virtual environment inside the docker for the
hafnium jobs.
Always use the python inside the venv.
This is so all scripts in hafnium use it.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: Ia8fec35761ba8249dda8f34a9cbd6b58f14af253
1 file changed