Avoid unnecessary warning log of sleep token

The updateKeyguardSleepToken can be called multiple times. e.g.
keyguardGoingAway and then setKeyguardShown. Then the sleep token
was removed by the first call. And the second call will always
print a warning: "Remove non-existent sleep token"

Bug: 423701190
Flag: EXEMPT skip warning log
Test: presubmit
Change-Id: Ib5f2f7241263fe19c0b85f5cf888509702a71ec1