test: fix test-evolve.t Metaedit take the current date when no date is given. When we added default- date, the date ended up to be the same and the behavior changed. Fix the text by disabling default-date in the metaedit call and update the comment about what is needed to fix correctly the test; take the changeset date when metaediting only one changeset.

# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)