Always only delete the install directory if it's empty.

We have to reset the force removal flag inside the operation
to not delete any other files/ folders than our own created.
Once the flag is set to false, the operation will fail on any
file/ folder still left in the install path.
Note: the config.rcc is a dummy file to calm down settings class
parser warnings.

Change-Id: I66efb5836e310bdb1b64e5647ee76c058cea2a7e
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>