discovery: only interpret remote announcements as pre-mature
discovery: only interpret remote announcements as pre-mature

This commit fixes a slight bug in the announcement processing logic
within the AuthenticatedGossiper. Before this commit, it was possible
for us to ignore one of our now announcements due to it being
pre-mature, rendering (atm) the channel unusable by the ChannelRouter
itself. To fix this, we know only check for a pre mature announcement
iff the message is coming from a remote node.

aakselrod/lnd,LightningNetwork/lnd,aakselrod/lnd,LightningNetwork/lnd