Improve arachni result polling mechanics

[J12934]

Improved how the scanner wrapper polls the arachni api server for the finished results.

• Use /scans/:scanId/summary instead of the full /scans/:scanId/ endpoint. This greatly reduced load on the api server as the responses are way smaller.
• In case of polling timeouts the wrapper will only fail if it gets 10 consecutive timeouts / errors. If the wrapper get a successful response the counter is reset.
• Increased polling timeout from 2 to 5 seconds and the final result fetch timeout from 2 to 60

[rseedorff]

Nice improvement! Thx for that