Properly disconnect on connection failure

[puddly]

The radio library currently leaves the serial connection open permanently now that we enforce exclusivity. This should fix instances of ZHA "not working" during adapter setup and requiring a full restart to start functioning again.

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 46.42%. Comparing base (eb4d141) to head (0848104).
Report is 1 commits behind head on dev.

Files with missing lines	Patch %	Lines
zigpy_zigate/zigbee/application.py	57.14%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #161      +/-   ##
==========================================
- Coverage   46.49%   46.42%   -0.07%     
==========================================
  Files           8        8              
  Lines        1297     1301       +4     
==========================================
+ Hits          603      604       +1     
- Misses        694      697       +3     

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