prevent SOCKET leak in BindListenPort()

- the call to CloseSocket() is placed after the WSAGetLastError(), because
  a CloseSocket() can trigger an error also, which we don't want for the
  logging in this two cases

src/net.cpp

@@ -1678,6 +1678,7 @@ bool BindListenPort(const CService &addrBind, string& strError, bool fWhiteliste
         else
             strError = strprintf(_("Unable to bind to %s on this computer (bind returned error %s)"), addrBind.ToString(), NetworkErrorString(nErr));
         LogPrintf("%s\n", strError);
+        CloseSocket(hListenSocket);
         return false;
     }
     LogPrintf("Bound to %s\n", addrBind.ToString());
@@ -1687,6 +1688,7 @@ bool BindListenPort(const CService &addrBind, string& strError, bool fWhiteliste
     {
         strError = strprintf(_("Error: Listening for incoming connections failed (listen returned error %s)"), NetworkErrorString(WSAGetLastError()));
         LogPrintf("%s\n", strError);
+        CloseSocket(hListenSocket);
         return false;
     }