fix(xen-api/putResource): use agent for both requests

[tkrafael]

Check list

Check if done, if not relevant leave unchecked.

• Fixes When using http proxy in xcp server, import vdi content fails #6260

• CHANGELOG.unreleased.md:

  • enhancement/bug fix entry added
  • list of packages to release updated (${name} v${new version})

• I have tested added/updated features (and impacted code)

  • unit tests (e.g. cron/parse.spec.js)
  • if xo-server API changes, the corresponding test has been added to/updated on xo-server-test
  • at least manual testing

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4. if necessary, update your PR, and re- add a reviewer

From the Four Agreements:

1. Be impeccable with your word.
2. Don't take anything personally.
3. Don't make assumptions.
4. Always do your best.