Narrow down issues with callstack tests #557

Currently we know the following:

• Running plain FF makes the stackDump API behave as expected.
• Running demo.py (or tests) and the JS Instrument enabled makes the stackDump API behave as expected.
• Running demo.py and no JS leads to the actors not being created in normal windows and only the children being created in privileged windows (DevTool, about:debugging) but even there no callstacks get captured
• Running raw selenium with no JS also leads to the above behaviour

Further suggested exploration:

• Run with a reduced config for non-debugging (prod) setup
• Inject more complex contentscript when running with OpenWPM

Resolution options:

• Find solution on friday
• Programmatically enforce in deployFirefox.py that the callstacks code doesn't run without both HTTP instrument and the JS instrument