title: getProperty & getSystemProperty in MonkeyRunner return None
body: <p>I'm new to Android development and test, currently I'm training to make a test scripts under Python and then use monkeyrunner to run them.</p>
  
  <p>As said in MonkeyDevice official documentation , the [getProperty()][1] and [getSystemProperty()][2] should return you a value that depends on property variable name you pass for them. Each time I got only 'None' value. Any idea or trick?!</p>
  
  <p>The simple code I'm using : </p>
  
  <pre><code>from com.android.monkeyrunner import MonkeyDevice,MonkeyRunner
  
  device = MonkeyRunner.waitForConnection()
  
  print device.getSystemProperty('version.sdk')
  </code></pre>
  
  <p>Regards,,,</p>