Allow running tests/parse.js offline by turning off fetchConfig.

If the API servers are heavily loaded, comparing times of --html2wt runs
of parse.js can be swamped by the variance in API request response times.
Allow using our cached config to remove this effect.

Change-Id: Iaaecaf33bfc5d7d24b7cfce33d791f64541463e5
Merge "Allow running tests/parse.js offline by turning off fetchConfig."