Squish: Small fixes for utils.py

* invokeMenuItem(): changed order and additional
  waitFor to be more error-proof on Mac
* logApplicationOutput(): added try/except block
  for cases where no former run/debug could be found

Change-Id: I0d434fbb964e3d85e5ccb2a4c336e14e956f44ce
Reviewed-by: Robert Löhning <robert.loehning@nokia.com>