[Role Logic Move] Make flag fixed

Make the 'role_controller_in_system_server' flag a 'fixed' flag.
The reason is that it may be used at boot time, before DeviceConfig
is available.

To toggle this flag on a local build, create this file locally:

    vendor/google/release/aconfig/trunk_staging/android.permission.flags
    /override_flag_values.textproto

...with the contents:

    flag_value {
        package: "android.permission.flags"
        name: "device_aware_permission_apis"
        state: ENABLED
        permission: READ_ONLY
    }

...and change 'state' to 'ENABLED' or 'DISABLED'. Then build and
re-flash.

Test: manual
Fix: 310718277
Change-Id: I31599008f0053008cc01442b663eae4a6c006aa8