Kernel: Detect some outgoing TCP connection failures

Author: https://github.com/deoxxa
Commit: fc3667c026
Pull-request: https://github.com/SerenityOS/serenity/pull/429

Kernel/Net/TCPSocket.cpp

@@ -274,6 +274,8 @@ KResult TCPSocket::protocol_connect(FileDescription& description, ShouldBlock sh
         if (current->block<Thread::ConnectBlocker>(description) == Thread::BlockResult::InterruptedBySignal)
             return KResult(-EINTR);
         ASSERT(setup_state() == SetupState::Completed);
+        if (has_error())
+            return KResult(-ECONNREFUSED);
         return KSuccess;
     }