Badger fails to notify after RDP session

[jeffmelville]

If the computer has been accessed remotely, badger will fail to notify subsequent events without being restarted.

[jeffmelville]

('Failed to list readers', -2146435042L)
<traceback object at 0x0336C0F8>
<class 'smartcard.Exceptions.ListReadersException'>
('Failed to list readers', -2146435042L)
<traceback object at 0x0336C3F0>
<class 'smartcard.Exceptions.ListReadersException'>

[jeffmelville]

Proposed fix:

• Add a Reader observer and keep track of # of readers
• Stop card observer when 0 readers
• Restart card observer when > 0 readers again