moxi: binary sasl auth on gateway moxi sometimes doesn't work

here, you can see the client is sometimes getting the item from the wrong bucket (the default bucket)...

>>> c = mc_bin_client.MemcachedClient(port=11211)
>>> c.sasl_auth_plain('mcbucket2', 'password')
(3693405178, 0, 'Authenticated')
>>> c.get('a')
(0, 1, 'dd')
>>> c = mc_bin_client.MemcachedClient(port=11211)
>>> c.sasl_auth_plain('mcbucket2', 'password')
(1306703597, 0, 'Authenticated')
>>> c.get('a')
(0, 4, 'on-mcbucket2!')
>>>