IFW: check that installerbase is not found from install root

When running qt installer or maintenancetool with update to new maintenancetool, installer extracts installerbase(.exe) to the root directory and after installation it is used as a base to new maintenancetool. Afer that nstallerbase(.exe) should be deleted.
Once the installation is complete make sure the installerbase(.exe) is not found in install root.