Fix test case deprecation warnings

[kashifpk]

When running test cases on ubuntu dev setup I get deprecation warnings which will cause errors starting from python 3.10.

PYTHONPATH=./ pytest --cov=minerconfig --cov=lib                                                                                             
============================================================= test session starts ==============================================================
platform linux -- Python 3.8.10, pytest-6.2.4, py-1.11.0, pluggy-0.13.1
rootdir: /MyWork/Nebra/code/hm-config                                   
plugins: cov-2.12.1                                                     
collected 47 items                                                                                                                              
                                                                        
tests/gatewayconfig/test_file_loader.py .....                                                                                            [ 10%] 
tests/gatewayconfig/test_gatewayconfig_app.py .                                                                                          [ 12%] 
tests/gatewayconfig/test_gatewayconfig_shared_state.py ..                                                                                [ 17%] 
tests/gatewayconfig/bluetooth/test_bluetooth_connection_advertisement.py .................                                               [ 53%] 
tests/gatewayconfig/bluetooth/test_diagnostics_characteristic.py .                                                                       [ 55%] 
tests/gatewayconfig/processors/test_diagnostics_processor.py .                                                                           [ 57%] 
tests/lib/cputemp/test_ble_tools.py ....                                                                                                 [ 65%] 
tests/lib/cputemp/test_nmcli_custom.py ................                                                                                  [100%]/
MyWork/Nebra/venv/lib/python3.8/site-packages/coverage/inorout.py:516: CoverageWarning: Module minerconfig was never imported. (module-not-impor
ted)                                
  self.warn(f"Module {pkg} was never imported.", slug="module-not-imported")                                                                   
                                    

=============================================================== warnings summary ===============================================================
../../venv/lib/python3.8/site-packages/dbus/service.py:35
  /MyWork/Nebra/venv/lib/python3.8/site-packages/dbus/service.py:35: DeprecationWarning: Using or importing the ABCs from 'collections' instead 
of from 'collections.abc' is deprecated since Python 3.3, and in 3.10 it will stop working
    from collections import Sequence 

../../venv/lib/python3.8/site-packages/dbus/decorators.py:330
  /MyWork/Nebra/venv/lib/python3.8/site-packages/dbus/decorators.py:330: DeprecationWarning: inspect.getargspec() is deprecated since Python 3.0
, use inspect.signature() or inspect.getfullargspec()
    args = inspect.getargspec(func)[0]

tests/gatewayconfig/test_gatewayconfig_app.py::TestGatewayconfigSha::test_gpio_pins
  /MyWork/Nebra/code/hm-config/lib/cputemp/service.py:59: PyGIDeprecationWarning: GObject.MainLoop is deprecated; use GLib.MainLoop instead
    self.mainloop = GObject.MainLoop()

-- Docs: https://docs.pytest.org/en/stable/warnings.html

---------- coverage: platform linux, python 3.8.10-final-0 -----------
Name                           Stmts   Miss  Cover
--------------------------------------------------
lib/cputemp/advertisement.py      84      1    99%
lib/cputemp/bletools.py           40      9    78%
lib/cputemp/service.py           191     62    68%
--------------------------------------------------
TOTAL                            315     72    77%

======================================================== 47 passed, 3 warnings in 1.13s ========================================================

Since python 3.10 has already been released anyone using latest python (including upcoming ubuntu 22.04 LTS) will cause these tests to fail.

[vpetersson]

@kashifpk Yeah this is part of a bigger discussion. In short, we are going to unpin the Python packages in the Dockerfile.

[vpetersson]

Closed in favor of #127