Autoscale testcase-provided timeout to compensate for slooow machines
Each test case has a timeout to guard against runaway tests. However
on really slow machines the timeout us not big enough. To compensate for this,
asses the "speed" of machine running tests and scale default timeout
if machine is slower than some (arbitrary) norm.
The speed assesment is done by measuring time to run (arbitrary) benchmark
code. This has the advantage to reflect actual machine load, not only
hardvare spec.
However, we may need to play with these magic numbers to make it working.
Generally a workaround.