p2p/discover: fix two bugs in lookup iterator

The lookup would add self into the replyBuffer if returned by another node.
Avoid doing that by marking self as seen.

With the changed initialization behavior of lookup, the lookupIterator needs to yield the
buffer right after creation. This fixes the smallNetConvergence test, where all results
are straight out of the local table.

p2p/discover/lookup.go

@@ -53,6 +53,7 @@ func newLookup(ctx context.Context, tab *Table, target enode.ID, q queryFunc) *l
 	// Don't query further if we hit ourself.
 	// Unlikely to happen often in practice.
 	it.asked[tab.self().ID()] = true
+	it.seen[tab.self().ID()] = true
 
 	// Initialize the lookup with nodes from table.
 	closest := it.tab.findnodeByID(it.result.target, bucketSize, false)
@@ -186,8 +187,12 @@ func (it *lookupIterator) Next() bool {
 				// is in a degraded state, and we need to wait for it to fill again.
 				it.lookupFailed(it.lookup.tab)
 			}
+			// Otherwise, yield the initial nodes from the iterator before advancing
+			// the lookup.
+			it.buffer = it.lookup.replyBuffer
 			continue
 		}
+
 		newNodes := it.lookup.advance()
 		it.buffer = it.lookup.replyBuffer
 		if !newNodes {