Fix HMR hostname in browser

[jkrehm]

Fixes regression introduced in #921

[codecov-io]

Codecov Report

Merging #965 into master will increase coverage by 0.23%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #965      +/-   ##
==========================================
+ Coverage   89.75%   89.98%   +0.23%     
==========================================
  Files          68       68              
  Lines        3437     2717     -720     
==========================================
- Hits         3085     2445     -640     
+ Misses        352      272      -80

Impacted Files	Coverage Δ
src/Bundler.js	92.85% <ø> (ø)	⬆️
src/utils/objectHash.js	42.3% <0%> (-42.31%)	⬇️
src/assets/GlobAsset.js	58.66% <0%> (-40%)	⬇️
src/utils/config.js	59.42% <0%> (-28.99%)	⬇️
src/assets/RawAsset.js	71.42% <0%> (-21.43%)	⬇️
src/utils/md5.js	83.33% <0%> (-16.67%)	⬇️
src/utils/urlJoin.js	84.61% <0%> (-15.39%)	⬇️
src/utils/fs.js	88.23% <0%> (-11.77%)	⬇️
src/utils/is-url.js	88.88% <0%> (-11.12%)	⬇️
src/utils/promisify.js	77.77% <0%> (-11.12%)	⬇️
... and 31 more

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[jkrehm]

Thanks!