replace UserManagerInternal with UserManager

Because Bluetooth is going mainline, we need to remove call to hidden
API.
UserManagerInternal and UserRestrictionsListener are hidden, the
available alternative are UserManager and IUserRestrictionsListener

Bug: 211851706
Test: Build + start bt
Tag: #refactor
Change-Id: I804b2124634a18187c022293664614807535966e
1 file changed