Always allow system uid to update device stats

The system uid always have permission UPDATE_DEVICE_STATS but it cannot
be properly recognized by permissionMonitor since it is not a installed
package. Instead, netd should always allow the system uid to do the
action.

Fix: 128638982
Bug: 124004517
Test: NetworkUsageStatsTest
      "dumpsys netd trafficcontroller" show entries in counterSet map

Change-Id: I7214d7d9acd95bf514c4b6dad9f6d0659be6d571
1 file changed