Energy scanning improvements

[puddly]

The maximum-seen LQI is suspiciously 85, which is exactly 255 / 3, even with a EFR32 stick nearby performing a tone test at +20dBm.

For https://github.com/zigpy/zigpy/pull/1183

[MattWestb]

Then i was running RasBee with deCONZ i was having the impression that the coordinator is very dominant and was making end devices using it as parent. But my feeling was that it was asymmetric = RX and TX links was not the same so one end device can hearing the coordinator but the coordinator was not hearing the end device good. The best is having it balanced so the link is working good and the device can getting one true fact then shushing its parent.

Also the old IKEA Zigbee module (EFR32MG1P) was having +19 dBm and the new Silabs is only 16 dBm but i think the link symmetric is better.

Silabs have one test paper with routers and end device explaining how its working in real with sleeping end device that is using 1/10 or power and and routers covering for getting them retching out from "radio clouds" but i cant finding it for the moment but is abut radio performance in Zigbee mesh networks.

[codecov-commenter]

Codecov Report

Patch coverage: 33.33% and project coverage change: -0.19 :warning:

Comparison is base (80041b9) 98.00% compared to head (1b788a6) 97.82%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #216 +/- ## ========================================== - Coverage 98.00% 97.82% -0.19% ========================================== Files 6 7 +1 Lines 1003 1011 +8 ========================================== + Hits 983 989 +6 - Misses 20 22 +2 ``` | [Impacted Files](https://codecov.io/gh/zigpy/zigpy-deconz/pull/216?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy) | Coverage Δ | | |---|---|---| | [zigpy\_deconz/zigbee/application.py](https://codecov.io/gh/zigpy/zigpy-deconz/pull/216?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy#diff-emlncHlfZGVjb256L3ppZ2JlZS9hcHBsaWNhdGlvbi5weQ==) | `98.07% <33.33%> (-0.63%)` | :arrow_down: | ... and [1 file with indirect coverage changes](https://codecov.io/gh/zigpy/zigpy-deconz/pull/216/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy) Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy)

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