The request/response interception has not yet been used, and
introduced quite a bit of complexity, especially surrounding fetchMock.
Furthermore, they made our DSVM tests fail, as the browser's implementation
of Request requires that a request body be accessed using the regular
json(), text(), etc. promise generators. Since this would have
simply added more complexity to an already complex, unused feature,
we've simply removed the feature.
Change-Id: I4cdf7b7106c771f0562de47e8835076d48d03a31
7767d0183c