QtIFW

Fix installer hang on Windows with empty command prompt window appearing

Installer sometimes hangs on Windows with a command prompt window opening
and blocking any progress. Hitting enter in this command prompt window
causes progress to move forward. This blocks automated execution of tests
since it requires manual interaction.

parentConsole boolean was not initialized properly, fix logically broken
closing actions for console.

Task-number: QTIFW-1250
Change-Id: I062c0491c16c26e9435022d79f99240bf59e1a79
Reviewed-by: Katja Marttila <katja.marttila@qt.io>