misc coverity issues

:Release Notes:
Scrub the issues reported by coverity tool.

:Detailed Notes:
- handle command-line parsing error respectively
- eliminate lstat() used together with unlink()

:Testing Performed:

:QA Notes:

:Issues Addressed:
[GF-52225] luna-sysservice: Coverity reports Medium and Low impact issues

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>

Change-Id: I515090b911497f8524865f83f802c9bfce2fc77e
Reviewed-on: https://g2g.palm.com/3990
Reviewed-by: DCO Verification
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Tested-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>