Gets mongo version of the server if it is running. Otherwise return
         version configured in mongoVersion property

def get_mongo_version(self):
        """
        Gets mongo version of the server if it is running. Otherwise return
         version configured in mongoVersion property
        """
        if self._mongo_version:
            return self._mongo_version

        mongo_version = self.read_current_mongo_version()

        if not mongo_version:
            mongo_version = self.get_configured_mongo_version()

        self._mongo_version = mongo_version

        return self._mongo_version