vmproxy: always set Host header from VMURL

[r3code]

closes #3635

PMM-0

Link to the Feature Build: SUBMODULES-0

If this PR adds or removes or alters one or more API endpoints, please review and add or update the relevant API documents as well:

• API Docs updated

If this PR is related to some other PRs in this or other repositories, please provide links to those PRs:

• Links to related pull requests (optional).

[codecov]

Codecov Report

Attention: Patch coverage is 91.42857% with 3 lines in your changes missing coverage. Please review.

Please upload report for BASE (v3@d5d500b). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
vmproxy/proxy/proxy.go	91.42%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##             v3    #3636   +/-   ##
=====================================
  Coverage      ?   43.67%           
=====================================
  Files         ?      366           
  Lines         ?    44328           
  Branches      ?        0           
=====================================
  Hits          ?    19360           
  Misses        ?    23287           
  Partials      ?     1681           

Flag	Coverage Δ
vmproxy	73.45% <91.42%> (?)

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