serve: respect settings from .hg/hgrc
create_server was looking only at the root ui object, ignoring any
settings from .hg/hgrc. To keep respecting command-line arguments,
commands.serve must also call repo.ui.setconfig.
# should print nothing# should print ? b/x? b/x# should print A b/xA b/x# should forget b/xforgetting b/x# should print nothing