wait for cloud to actually stop the test on first '^C' (#1705)
wait for cloud to actually stop the test on first '^C' (#1705)

Also:
- move the signal handling as far up as possible
- stop the test in goroutine so if that takes a while a second ^C will
  again stop the test


Co-authored-by: na-- <d1854cae891ec7b29161ccaf79a24b00c274bdaa@andreev.sh>
loadimpact/k6,loadimpact/k6