add user-agent header to template downloader request

[sudo87]

Description

This PR adds user-agent header to download request.

Some template providers reject HTTP requests without a User-Agent
header and return HTTP 403 instead of redirecting to the actual
download location. This causes template downloads to fail.

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (improves an existing feature and functionality)
• Cleanup (Code refactoring and cleanup, that may add test cases)
• Build/CI
• Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

Screenshots (if appropriate):

How Has This Been Tested?

How did you try to break this feature and the system with this change?

[sudo87]

@blueorangutan package

[blueorangutan]

@sudo87 a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 17.61%. Comparing base (7aa0558) to head (1fe48e1).

Files with missing lines	Patch %	Lines
...cloud/storage/template/HttpTemplateDownloader.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               4.22   #12791      +/-   ##
============================================
- Coverage     17.61%   17.61%   -0.01%     
- Complexity    15664    15665       +1     
============================================
  Files          5917     5917              
  Lines        531402   531403       +1     
  Branches      64971    64971              
============================================
  Hits          93596    93596              
- Misses       427252   427253       +1     
  Partials      10554    10554              

Flag	Coverage Δ
uitests	3.70% <ø> (ø)
unittests	18.68% <0.00%> (-0.01%)	⬇️

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[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✖️ debian ✔️ suse15. SL-JID 17096

[weizhouapache]

@sudo87
code looks ok

any linked issue ?