discovery: explicitly check for None in outgoing init
f09d0004481c introduced default params for discovery.outgoing(), but it used a
falsy check instead of an explicit check for None. The result is that callers
that passed in an empty list would have that list overridden by the defaults,
which is not the expected behavior.
This was discovered by changes to the test-pushrebase.t test in Facebook's
repository of mercurial extensions.
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)