This reverts

    CmbIpc: Remove workaround
    287a2630



since the bug still exists. However, we use waitForBytesWritten()
instead of QCoreApplication::processEvents() since this seems to be fine
(QAbstractSocket::waitForBytesWritten is not called on Windows).

The bug was:
 1. Open a bigger project, like qtcreator.pro.
 2. After 2 seconds, quit it.
 ==> The Qt Creator window is gone but the Qt Creator process waits
     until the clangbackend process is finished.

Change-Id: I25c475d2a6db94a1c3a8d827a41f8c0b2624eaea
Reviewed-by: Marco Bubke <marco.bubke@theqtcompany.com>