Fix metainfo_example test

:Release Notes:
Fix metainfo_example test to unregister service
after mainloop is stopped

:Detailed Notes:

:Testing Performed:
Unit-tests

:QA Notes:

:Issues Addressed:
[CMB-559] metainfo_example crash in subscriptions

Open-webOS-DCO-1.0-Signed-off-by: Alexandr Smoktal <alexandr.smoktal@lge.com>

Change-Id: Ia5461922aae50794b3c38c84c1f9d6062ed1c774
Reviewed-on: https://g2g.palm.com/6277
Reviewed-by: DCO Verification
Reviewed-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Tested-by: Alexandr Smoktal <alexandr.smoktal@lge.com>
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Reviewed-by: Anatolii Sakhnik <anatolii.sakhnik@lge.com>