Validate json data

:Release Notes:
PmLogMsgKS_() will validate json data whether it has right format

:Detailed Notes:
The variable final_str in function PmLogMsgKS_() includes
key-value pairs and free text string. The new routine splits
key-value pairs(json) and free text string, then uses the existing
fucntion validate_json_string for validation.

:Testing Performed:
Compiled locally and tested on local and TV.
Verified in the log file, error text displayed in
/var/log/legacy-log properly.

:QA Notes:

:Issues Addressed:
[GF-10575] key-value pair should be in proper json format

Open-webOS-DCO-1.0-Signed-off-by: Hongjeon Ha <hj.ha@lge.com>

Change-Id: I4d5107beaf333ac0f2fe862147ba8e33434c6e0e
Reviewed-on: https://g2g.palm.com/2934
Reviewed-by: Build Verification
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Tested-by: Keith Derrick <keith.derrick@lge.com>