Fix coverity issues

:Release Notes:
Fix `fscanf` precision.
Fix strings deallocation.

:Detailed Notes:

:Testing Performed:
Modified functions was tested by hands.

:QA Notes:

:Issues Addressed:
[GF-53047] Luna-prefs: fix coverity issues

Open-webOS-DCO-1.0-Signed-off-by: Alexandr Smoktal <alexandr.smoktal@lge.com>

Change-Id: If1f1c92c6873d124cc45efc4a1be6f46bf10c24b
Reviewed-on: https://g2g.palm.com/4064
Reviewed-by: DCO Verification
Reviewed-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Tested-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>