Prohibit showing system decorations on untrusted virtual displays

Enable "Force destop mode" will enable system decorations on all
virtual displays and system will put launchers on untrusted virtual
displays.

This is to prohibit showing system decorations on untrusted virtual
displays for "Force desktop mode".

Change-Id: Ibcda42291ed51157172fdbb192f46f16bef91162
Bug: 130264203
Test: atest MultiDisplaySystemDecorationTests