VcsCommand: Block auto reload while a command is running

Git rebase is executed in the background, and it can change a file multiple
times in a short period. If we reparse a file while this happens on
Windows, Git fails to replace it, the rebase action fails and the
repository becomes unstable (remains with a modified file).

See discussion at https://github.com/git-for-windows/git/pull/1666

Task-number: QTCREATORBUG-15449
Change-Id: Iba40a770a1df2dfff0dd1c874c491dfbe1cceb58
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/shellcommand.cpp

@@ -276,6 +276,7 @@ void ShellCommand::run(QFutureInterface<void> &future)
     QString stdOut;
     QString stdErr;
 
+    emit started();
     if (d->m_progressParser)
         d->m_progressParser->setFuture(&future);
     else