Fix alarm manager FGS reason codes

The reason code for alarm_clock was never used as intended. This means
we cannot differentiate between the two types in metrics.
Also fixing the reason code to be used while denying fgs. This should
not cause any functional change but is better for consistency and
catching inadvertent bugs in the future.

Test: atest CtsAlarmManagerTestCases:ExactAlarmsTest
./out/host/linux-x86/bin/statsd_testdrive 60
Should show reason code 301 after running
ExactAlarmsTest#alarmClockAllowsFGS

Bug: 231661615
Change-Id: I8c20f6b040d9fbdb0808769a4fa0eae7c63d5e07