Need use 'nonplat_service_contexts_file' as the file context for
/vendor_service_context on non full-treble device.
Otherwise, servicemanager can't read the file.

Bug: 72787689
Test: build
Change-Id: Ib54e4f2501c7bbf8b397eacf4afadfae344ddd03
(cherry picked from commit 37d474f0)