Updated build of tango dummy-cs

[JeanLucPons]

This PR solves issue when switching between dummy-cs and true tango cs.

[gubaidulinvadim]

I actually fail to reproduce the issue either here or on the main branch. @TeresiaOlsson, could you check that there's no conflict anymore with tango?

[JeanLucPons]

To reproduce the issue on the main you should:
Make a succesfull test using a true control system.
Install the dummy cs:

pip install tests/dummy_cs/tango-pyaml

then it breaks tango:

>>> import tango
>>> ds = tango.DeviceProxy("1/2/3")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'tango' has no attribute 'DeviceProxy'

To go back in a clean situation you have to uninstall all (tango-pyaml and pytango) and reinstall.

This PR prevents to break tango and to switch between tests/dummy_cs/tango-pyaml and tango-pyaml

[TeresiaOlsson]

I actually fail to reproduce the issue either here or on the main branch. @TeresiaOlsson, could you check that there's no conflict anymore with tango?

I don't understand. What should I check? I have had no issues with dummy-cs because I never tried to run any of the tests.

[JeanLucPons]

It would be nice that this patch is applied.
It is annoying when you switch from true to dummy CS to reinstall all each time.
Thanks.

[TeresiaOlsson]

Should this work now? I just pull the latest version of the main branch and I have the problem.

I have the problem when trying to run the scripts in the examples folder if that makes a difference?