CMakeLists: enable UNITTEST flags

:Release Notes:

:Detailed Notes:
Turn on UNITTEST when global WEBOS_CONFIG_BUILD_TESTS flag are enable

:Testing Performed:
Testing on local environment

:QA Notes:

:Issues Addressed:

Open-webOS-DCO-1.0-Signed-off-by: Maksym Sditanov <msditanov@luxoft.com>

Change-Id: Ia639d531c0dd66a9e5d8b02d7a6e53621b04558f
Reviewed-on: https://g2g.palm.com/2955
Reviewed-by: Build Verification
Reviewed-by: Maksym Sditanov <msditanov@luxoft.com>
Tested-by: Maksym Sditanov <msditanov@luxoft.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>