Fix time calculation in performance tests.

:Release Notes:
Time calculation performed using "clock_gettime()" function.

:Detailed Notes:
Using "clock_gettime()" function instead of MojTime class.
Added total elapsed time for testing in seconds.

:Testing Performed:
Tested on locale build.

:QA Notes:

:Issues Addressed:
[BHV-3244] Fix time calculation in performance tests.

Open-webOS-DCO-1.0-Signed-off-by: Iurii Artemenko <iurii.artemenko@lge.com>

Change-Id: If1c1c31cbe0d56df882e6bcdd30ad4c352351065
Reviewed-on: https://g2g.palm.com/5176
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>