p2p: Add timeout for AddrFetch peers

If AddrFetch peers don't send us addresses, disconnect them after
a while.

Author: mzumsande

src/net_processing.cpp

@@ -4364,6 +4364,12 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
 
     const auto current_time = GetTime<std::chrono::microseconds>();
 
+    if (pto->IsAddrFetchConn() && current_time - std::chrono::seconds(pto->nTimeConnected) > 10 * AVG_ADDRESS_BROADCAST_INTERVAL) {
+        LogPrint(BCLog::NET, "addrfetch connection timeout; disconnecting peer=%d\n", pto->GetId());
+        pto->fDisconnect = true;
+        return true;
+    }
+
     MaybeSendPing(*pto, *peer, current_time);
 
     // MaybeSendPing may have marked peer for disconnection