Don't load nonplat_service_contexts on full-treble.

On full Treble devices, servicemanager should only
host services served from processes on /system; don't load
nonplat_service_contexts.

Bug: 36866029
Test: builds, boot Taimen, boot Sailfish
Change-Id: Ia093c4c6b342335e35648db35e340e2df54fdcf3
Merged-In: Ia093c4c6b342335e35648db35e340e2df54fdcf3
(cherry picked from commit e3ab0e60863e9df66fdf59c400f6065b21c01ec9)
2 files changed