net: only disconnect if fDisconnect has been set

These conditions are problematic to check without locking, and we shouldn't be
relying on the refcount to disconnect.

src/net.cpp

@@ -1051,8 +1051,7 @@ void CConnman::ThreadSocketHandler()
             std::vector<CNode*> vNodesCopy = vNodes;
             BOOST_FOREACH(CNode* pnode, vNodesCopy)
             {
-                if (pnode->fDisconnect ||
-                    (pnode->GetRefCount() <= 0 && pnode->vRecvMsg.empty() && pnode->nSendSize == 0))
+                if (pnode->fDisconnect)
                 {
                     // remove from vNodes
                     vNodes.erase(remove(vNodes.begin(), vNodes.end(), pnode), vNodes.end());