Fix purgeShardObject crash

:Release Notes:
Fix kinds cleanup (ignore built-in kinds);
old code removed.

:Detailed Notes:
Add verification for built-in kinds before cleanup;
removed not actual code for transient storage cleanup.

:Testing Performed:
tested on build

:QA Notes:
luna-send -f -n 1 -a com.palm.activitymanager luna://com.palm.db/purge '{}'

:Issues Addressed:
[GF-53753] Segment fault in MojDbShardEngine::purgeShardObject function
when db8 received purge activity from activity manager.

Open-webOS-DCO-1.0-Signed-off-by: Igor Kuksyuk <igor.kuksiuk@lge.com>

Change-Id: I967c59f202ae59de15e14c4a5d0940d1df958ca1
Reviewed-on: https://g2g.palm.com/4105
Reviewed-by: DCO Verification
Reviewed-by: Igor Kuksyuk <igor.kuksiuk@lge.com>
Tested-by: Igor Kuksyuk <igor.kuksiuk@lge.com>
Reviewed-by: Maksym Sditanov <maxim.sditanov@lge.com>
Tested-by: Maksym Sditanov <maxim.sditanov@lge.com>