deploy: Fix the issue of overlay unpack if the OS value is present

OS variable in the LAVA job definition will invoke the posix value even after the addition of lava_test_results_dir in the context session, So the overlay unpack is not happening in the specified custom path.

This will misplace the lava-test-runner as well, the patch will take the lava_test_results_dir from the job definition if exists or else will go for the posix value.

Signed-off-by: sarath P T sarath.pt@siemens.com