[net] Remove assert(nMaxInbound > 0)

nMaxInbound might very well be 0 or -1, if the user prefers to keep
a small number of maxconnections.

Note: nMaxInbound of -1 means that the user set maxconnections
to 8 or less, but we still want to keep an additional slot for
the feeler connection.

Github-Pull: #2682
Rebased-From: 72dfebb

Author: MarcoFalke

src/net.cpp

@@ -1037,7 +1037,6 @@ void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
     CAddress addr;
     int nInbound = 0;
     int nMaxInbound = nMaxConnections - (nMaxOutbound + nMaxFeeler);
-    assert(nMaxInbound > 0);
 
     if (hSocket != INVALID_SOCKET)
         if (!addr.SetSockAddr((const struct sockaddr*)&sockaddr))