Pubsub should not return messages from local peer.

[ralexstokes]

It looks like pubsub w/ gossipsub router yields messages we publish on the local peer to the local peer. This seems to be because we are using the same infrastructure to publish data as we are to read incoming data.

In particular, review use of self.subscribed_topics_receive[topic_id]. It seems like this is the only way right now to get gossip messages from others, but given the call to notify subscriptions in push_msg, we end up getting a reference to the message back locally.

[ralexstokes]

i think the correct place to handle this right now is to only execute this line:

py-libp2p/libp2p/pubsub/pubsub.py

Line 601 in 5144ab8

self.notify_subscriptions(msg)

if the message is not from the local peer.