git_cache: Add tests for reset fetch config.
git_cache: Add tests for reset fetch config.

Bug: 862547
Change-Id: I56b096cbf3358c06aa5c285594330af118ab17fd
Reviewed-on: https://chromium-review.googlesource.com/1138714
Commit-Queue: Edward Lesmes <d05609f027dc667cc37492b1dc1bdea5d60fa82a@chromium.org>
Reviewed-by: Aaron Gable <bbed39beedae4cdb499af742d2fcd6c63934d93b@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools