changegroup: clear progress callback after changelog processing The progress callback is replaced by one for manifests after changelog processing is done, but let's not depend on manifests replacing the value and instead explicitly clear it.

tests: adjust for code move in Hypothesis 2.0.0 It appears that the Settings class was renamed to settings, and because of this, the settings module was renamed to configuration. https://github.com/DRMacIver/hypothesis/commit/a0e663b