Make system-as-root a phone-specific thing

Test: auto builds, boots
BUG: 110695415
Change-Id: Iffe8863e0a99e1dccb3325a6e5004e44a93e68f1
Merged-In: Iffe8863e0a99e1dccb3325a6e5004e44a93e68f1
(cherry picked from commit 512dad95b77e734435ce91043a2c1424d66eed19)
8 files changed