Fix checking of disallowed types during schema validation

:Release Notes:
The disallowed types validation is already implemented in
schema validation code, but it didn't work correctly.
Disallowed types checking is fixed

:Detailed Notes:
Fixed initialisation of disallowed types field in schema validator

:Testing Performed:
Unit tests succeeded. Added unit tests to cover disallowed types
validation

:QA Notes:

:Issues Addressed:
[GF-12798] pbnjson: disallowed types in schema validation doesn't work

Open-webOS-DCO-1.0-Signed-off-by: Mykola Kryvonos <mykola.kryvonos@lge.com>

Change-Id: I45679dbf62c34bc28a1ea199770548deffe1226d
Reviewed-on: https://g2g.palm.com/3025
Reviewed-by: Build Verification
Reviewed-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Tested-by: Mykola Kryvonos <mykola.kryvonos@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>