scripts: dont use the shell to get properties

Change-Id: If97aec9e1c03840cfcd22543c41a0e8ba3def6aa
input: change way to detect force navigation bar

do not show, if the device has a real navigation bar.
do not show, if we are on nameless, as we have force navbar built-in.

Change-Id: I27f85b75811933dc01ed915dfccf67e07b523ac6