[BUG] z dwell time checked when checking if we want to do a preflight, even for non-z protocols #671

(10.160710895153072, 'spoolController.StartSpooling', {'maxFrames': 10, 'protocol': 'htsms-widefield.py'}, 1.7976931348623157e+308, 200.0), spoolController.StartSpooling
DEBUG:PYME.Acquire.SpoolController:Looking for Bergamot/2020_12_4/PKfirst8wellibidi/000/4_12_series_D (.pcs or .h5) on cluster

Traceback (most recent call last):
  File "c:\users\bergamot\code\python-microscopy\PYME\ui\mytimer.py", line 42, in Notify
    a()
  File "c:\users\bergamot\code\python-microscopy\PYME\Acquire\ActionManager.py", line 140, in Tick
    self.isLastTaskDone = fcn(**args)
  File "c:\users\bergamot\code\python-microscopy\PYME\Acquire\SpoolController.py", line 415, in StartSpooling
    if doPreflightCheck and not preflight.ShowPreflightResults(None, protocol.PreflightCheck()):
  File "c:\users\bergamot\code\python-microscopy\PYME\Acquire\protocol.py", line 117, in PreflightCheck
    if not eval(c.check):
  File "<string>", line 1, in <module>
AttributeError: 'TaskListProtocol' object has no attribute 'dwellTime'