Format 'stopping motor...' more neatly when wait = True

[jmsv]

Format 'stopping motor...' more neatly when wait = True:

Fancy threading stuff happens when wait is True to make the method return immediately while the motor keeps spinning until the duration ends. This means that when stop is called at the end, the message printed (if verbose) is formatted badly:

In this case, the print statement prints to the Python console prompt, which shouldn't happen