Xhr unit tests intermittently fail on IE11

[bryanforbes]

Bug

When running the unit tests on IE11, the following error is intermittently raised:

× internet explorer 11 on WINDOWS - request/providers/xhr - Web Workers - from blob (0.001s)
    TypeError: Attempt to detect unregistered has feature "web-worker-xhr-upload"
      at has  <node_modules/@dojo/has/has.ts:239:2>
      at from blob  <tests/unit/request/xhr.ts:567:4>
      at Anonymous function  <node_modules/intern/browser/remote.js:56:10887>
      at Anonymous function  <node_modules/intern/browser/remote.js:6:4455>
      at i  <node_modules/intern/browser/remote.js:56:27528>
      at Anonymous function  <node_modules/intern/browser/remote.js:46:5856>
      at Anonymous function  <node_modules/intern/browser/remote.js:46:5622>
      at r  <node_modules/intern/browser/remote.js:56:27750>
      at Anonymous function  <node_modules/intern/browser/remote.js:56:28694>
      at r  <node_modules/intern/browser/remote.js:56:27750>

This is because of the has test added to keep the test from failing because of blobs passed to web workers failing in IE11

Package Version: master