Currently Tigase operates s2s socket in uni-directional mode, which can cause issues, with the other server has some limitations (for example doesn't accept s2s but itself opens s2s connections as in case of #servers-306). We shouldn't allow communication on such CID until connection is not established and authorised in both directions (in case BiDi is not supported, see #issue #1131)

NOTE: This should only apply in case of incomming connection (we make sure that we can't send response); we shouldn't really care in reverse case as we would be interested only in sending packets.