v2020 backport: sdk: Fix fallout of renaming chaiwala-tests

Backport of !155 (merged)

When some test scripts got moved from /usr/share/chaiwala-tests/ to /usr/lib/apertis-tests/ their path in the test definitions didn't get updated, causing the tests to fail:

+ common/run-test-in-systemd --basename --user=user -- /usr/share/chaiwala-tests/sdk/automated/test-valgrind.sh
/var/lib/lava-1826179/1/tests/6_sdk-debug-tools-valgrind/apertis-tests/common/tee-exec: 19: /var/lib/lava-1826179/1/tests/6_sdk-debug-tools-valgrind/apertis-tests/common/tee-exec: Job for generated-test-case-test-valgrind.service failed because the control process exited with error code./usr/share/chaiwala-tests/sdk/automated/test-valgrind.sh: not found

To fix the issue, rather that using the version shipped in /usr/lib/apertis-tests/ use the one in the git repository since we already have it checked out.