Fix tests when path location of yarn contains spaces

[Keraito]

Summary

If the path location for Yarn contains spaces, the test suite would fail on a command. The corresponding upstream issue on Node is nodejs/node#6803. This specific comment noted that the path should be escaped with double quotes.

Test plan

1. The path location to Yarn needs to contain spaces.
2. Run yarn run test.
3. Observe a command fail with a corrupted path location.

[bestander]

Much appreciated, thanks