Ignore the preferredModeId for non-focussed windows

If a window sets preferredModeId, and then enters pip mode. Then if the
mode/refresh-rate/resolution is chosen by user from Settings menu, it doesn't take
effect because of preferredModeId of the pip window.

Bug: 232711732
Test: atest DisplayContentTests
Change-Id: Ief48c38ff9dc85c9033d502cc4006130678ae808