IoTaC.get_device_list add unrelevant data to request parameters

[djs0109]

Describe the bug
With the following code, unrelevant data will as parameter with the request. And the actual relevant limit and offset are not being sent.

        params = {key: value for key, value in locals().items() if value is not
                  None}

To Reproduce
Add a breakpoint here

FiLiP/filip/clients/ngsi_v2/iota.py

Line 358 in 70006d6

try:

and run test_ngsi_v2_iota.py in debug mode and check the params