Go 1.7: Fix fetch_test.
Go 1.7: Fix fetch_test.

Somehow http://localhost:??? gets converted to http://localhost??? which gets
a real response.

BUG=

Review-Url: https://codereview.chromium.org/2355743006

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go