Improve gateway get_devices_from_dict

[starkillerOG]

Improve the get_devices_from_dict function of the gateway:
Now the device_id from direct communication is checked against the device_id received from the cloud.
Besides the already presend mac matching.
The _did is removed from the gateway since it is the same as the device_id which was already presend.

[starkillerOG]

@rytilahti could you review and merge?
(this was discovered during my work on the push server, but actually has nothing to do with the push server so I split it out).

[codecov-commenter]

Codecov Report

Merging #1456 (482a933) into master (4dd3cd8) will decrease coverage by 0.03%.
The diff coverage is 6.66%.

@@            Coverage Diff             @@
##           master    #1456      +/-   ##
==========================================
- Coverage   83.35%   83.32%   -0.04%     
==========================================
  Files         139      139              
  Lines       13670    13675       +5     
  Branches     3248     3249       +1     
==========================================
  Hits        11395    11395              
- Misses       2057     2062       +5     
  Partials      218      218              

Impacted Files	Coverage Δ
miio/gateway/gateway.py	46.19% <6.66%> (-1.40%)	⬇️

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[starkillerOG]

@rytilahti thanks for the review, I have processed your feedback.
Could you have a look again?

[starkillerOG]

I think the test failure is unrelated

[rytilahti]

LGTM, please add a note to description on why/how this improves it, then this is ready to go.

[starkillerOG]

@rytilahti I updated the description of the PR, ready to go.