[CB-4568] Disable pop-up messages when running test "XHR to within-package 11kb asset."

When fetching a file from the local file system, the result status of
XMLHttpRequest should be compared to 0 for success instead of 200.
This is because the file and ftp schemes do not use HTTP result codes.

FYI:https://developer.mozilla.org/es/docs/XMLHttpRequest/Usar_XMLHttpReq
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