- Split per user version of getUserRestrictions into a separate method
in DPMS and make the per-user version return null if the admin
parameter is not a valid one.
- Update isAccessibilityServicePermittedByAdmin and
isInputMethodPermittedByAdmin to return false if the admin parameter
is not a valid one.
Bug: 27909087
Change-Id: I6f4cae6552cbfe02dc4a92b04eeeddf0314e0974