webos-image: Invent WEBOS_DISABLE_LS2_SECURITY setting

:Release Notes:
Add a new setting WEBOS_DISABLE_LS2_SECURITY to disable LS2 security

:Detailed Notes:
A new variable WEBOS_DISABLE_LS2_SECURITY can be used in bitbake configuration
files to disable LS2 security.
Default value of the variable(false) is weakly set in LS2's recipe

:Testing Performed:
Checked that the setting impacts the security configuration

:QA Notes:

:Issues Addressed:
[GF-39397] Add a new setting WEBOS_DISABLE_LS2_SECURITY to disable LS2 security

Open-webOS-DCO-1.0-Signed-off-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>

Change-Id: I0ad1f53452881702b5c9a0b0ff0005592f062fd5
Reviewed-on: https://g2g.palm.com/3589
Reviewed-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>
Tested-by: Alekseyev Oleksandr <alekseyev.oleksandr@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>