Update _via_by_context earlier; fixes:
Traceback (most recent call last):
File "/Users/dmw/src/mitogen/mitogen/service.py", line 519, in _on_service_call
return invoker.invoke(method_name, kwargs, msg)
File "/Users/dmw/src/mitogen/mitogen/service.py", line 253, in invoke
response = self._invoke(method_name, kwargs, msg)
File "/Users/dmw/src/mitogen/mitogen/service.py", line 239, in _invoke
ret = method(**kwargs)
File "/Users/dmw/src/mitogen/ansible_mitogen/services.py", line 454, in get
reraise(*result)
File "/Users/dmw/src/mitogen/ansible_mitogen/services.py", line 412, in _wait_or_start
response = self._connect(key, spec, via=via)
File "/Users/dmw/src/mitogen/ansible_mitogen/services.py", line 363, in _connect
self._update_lru(context, spec, via)
File "/Users/dmw/src/mitogen/ansible_mitogen/services.py", line 266, in _update_lru
self._update_lru_unlocked(new_context, spec, via)
File "/Users/dmw/src/mitogen/ansible_mitogen/services.py", line 253, in _update_lru_unlocked
if self._refs_by_context[context] == 0:
KeyError: Context(1008, u'ssh.localhost.sudo.mitogen__user3')
d280bba02b