serviceWorkerRegistration.ts Unit Test

[lindsayJohnstonPnnl]

1. Create Jest tests for this component
2. Run yarn test --coverage --watchAll=false path/to/your/testfile.test.tsx to generate the test coverage report
3. Make your tests cover 80% of the statements, branches, functions and lines in the component according to the Jest coverage report
4. Add the Jest Coverage output to this wiki page under the Current Test Coverage heading to track our progress. (Replace any older reports under that heading but don't delete the original report from 3/11/15.)
5. Attach Jest coverage output to the PR