Replace md5 module with hashlib

fix following pylint error:

************* Module connectors.ConnectorBase
connectors/ConnectorBase.py:7: [W1648(bad-python3-import), ] Module moved in Python 3
************* Module runtime.PLCObject
runtime/PLCObject.py:33: [W1648(bad-python3-import), ] Module moved in Python 3

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
  <TargetType>
    <Linux/>
  </TargetType>
</BeremizRoot>