qt, rpc: Accept stop RPC even another command is executing

While here, clean up the command input by calling the trimmed function
on the input from the command prompt.

src/qt/rpcconsole.cpp

@@ -924,7 +924,7 @@ void RPCConsole::setMempoolSize(long numberOfTxs, size_t dynUsage)
 
 void RPCConsole::on_lineEdit_returnPressed()
 {
-    QString cmd = ui->lineEdit->text();
+    QString cmd = ui->lineEdit->text().trimmed();
 
     if (cmd.isEmpty()) {
         return;
@@ -942,6 +942,13 @@ void RPCConsole::on_lineEdit_returnPressed()
         return;
     }
 
+    // A special case allows to request shutdown even a long-running command is executed.
+    if (cmd == QLatin1String("stop")) {
+        std::string dummy;
+        RPCExecuteCommandLine(m_node, dummy, cmd.toStdString());
+        return;
+    }
+
     ui->lineEdit->clear();
 
 #ifdef ENABLE_WALLET