Enforce AllowNTPTime to disable all NTP requests

:Release Notes:
AllowNTPTime controls all NTP request and process of synchronization.

:Detailed Notes:
Added check for isNTPAllowed() into:
- updateSystemTime() // when automatic time synchronization requested
- handling getNTPTime()
- processing clockChanged() notification

:Testing Performed:
Verified in desktop build.

:QA Notes:

:Issues Addressed:
[GF-56211] Switch off NTP time synchronization when AllowNTPTime is false

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Change-Id: Ic3d8d298cdc405db98dbc152c0db873ba14c8b83
Reviewed-on: https://g2g.palm.com/4240
Reviewed-by: DCO Verification
Reviewed-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Tested-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>
Reviewed-by: Keith Derrick <keith.derrick@lge.com>