fix: use websocket hostname for server binding

[bbangert]

Closes #1004

[codecov-io]

Codecov Report

Merging #1005 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1005      +/-   ##
==========================================
+ Coverage   99.78%   99.79%   +0.01%     
==========================================
  Files          57       57              
  Lines        9593    10455     +862     
==========================================
+ Hits         9572    10434     +862     
  Misses         21       21

Impacted Files	Coverage Δ
autopush/websocket.py	100% <0%> (ø)	⬆️
autopush/router/webpush.py	100% <0%> (ø)	⬆️
autopush/tests/test_websocket.py	100% <0%> (ø)	⬆️
autopush/config.py	100% <0%> (ø)	⬆️
autopush/tests/test_main.py	100% <0%> (ø)	⬆️
autopush/tests/test_router.py	100% <0%> (ø)	⬆️
autopush/main_argparse.py	100% <0%> (ø)	⬆️

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