Trace duration on Sysconfig.readAllPermissions().

On automotive's reference implementation it can take up to 500ms, although
during this CL tests it took just 56ms:

10-22 16:14:53.241 30451 30525 D SystemConfig: readAllPermissions took to
complete: 56ms

Bug: 143112379
Test: adb logcat SystemConfig *:s

Change-Id: I21462482cd8d6d595220af716bbe6547c7637e49