installer: fix replacing executable name in Mac
installer: fix replacing executable name in Mac

Installer executable filename does not have suffix so
use the whole file name as search string when
updating the maintenance tool Info.plist file.

Task-number: QTBUG-26900

Change-Id: I8fd7c981fa9490fc1882b78ec08da81c59dc7428
Reviewed-by: Niels Weber <df24410c43e1f71d7f720aa26e4fcb77ce70f242@digia.com>
Reviewed-by: Tim Jenssen <6a21f175c697b4129e1bafb6e9b52078bb1a6738@digia.com>

olear/qtifw,olear/qtifw,olear/qtifw,olear/qtifw