asyncout-773313: Use test.checkCalled for async output
asyncout-773313: Use test.checkCalled for async output

We are now in a position to check delayed test output using our shiny
new checkCalled test harness feature.

Signed-off-by: Joe Walker <7a17872fbb32c7d760c9a16ee3076daead11efcf@mozilla.com>

mozilla/gcli,joewalker/gcli,joewalker/gcli,mozilla/gcli,mozilla/gcli