scripts/autobuilder-worker-prereq-tests: Shore up qemu testing
Check that yocto-autobuilder-helper has been cloned to the correct location.
Check that vnc is running using the same script the autobuilder does.
Set the DISPLAY enviroment variable to :1 the same way we do when building
normally.
Make the VM's serial console available so we can log in and power off allowing
the tests to continue.
Signed-off-by: Michael Halstead <mhalstead@linuxfoundation.org> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
