tests: fix style issue of importing hgweb in embedded code fragments Some test scripts are excluded in test-check-module-imports.t, because import-checker.py reports that hgweb and/or hgwebdir of mercurial.hgweb are not imported in recommended style. To fix this issues, this patch make python code fragments embedded in these files import hgweb from mercurial package at first, and refer hgweb and hgwebdir via imported hgweb.