Fix polling methods to return values instead of None
Fixed four polling-related methods in DeviceImpl that were calling their wrapper functions but not returning the results:
- is_attribute_polled(): was returning None instead of bool
- is_command_polled(): was returning None instead of bool
- get_attribute_poll_period(): was returning None instead of int
- get_command_poll_period(): was returning None instead of int
The issue was in the lambda functions in device_impl.cpp where the wrapper methods were called but the return statement was missing.
This fixes the bug where is_attribute_polled() would always return False even for polled attributes, and similar issues with the other methods