Fix multithreading issues with jschema_all()

:Release Notes:
Static instance of jschema_all() shouldn't be reference-counted.

:Detailed Notes:
Prevent potential race conditions in reference counting in
jschema_copy() and jschema_release(), when working with jschema_all().
Remove not used debugging code.

:Testing Performed:
Unit tests with memory checker.

:QA Notes:

:Issues Addressed:
[ANG-262] pbnjson: Fix potential multithreading issues in copy/release(jschema_all())

Open-webOS-DCO-1.0-Signed-off-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>

Change-Id: Ib6f0d1f95bbe07082768e8a01d0d39ed85addc17
Reviewed-on: https://g2g.palm.com/4442
Reviewed-by: DCO Verification
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Tested-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>
Reviewed-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Reviewed-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>