Add option to disable iallocator use in QA

By default some QA tests use iallocators. It is now possible to disable
iallocators in QA, so that QA doesn't force having iallocators set up.
The affected tests have now alternatives pathways.

Signed-off-by: Bernardo Dal Seno <bdalseno@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>