Fix accounting of open wakelocks

This fixes a discrepancy discovered when cross-validating
against existing telemetry metrics.

Bug: 380847722
Test: com.android.server.power.stats.WakelockStatsFrameworkEventsTest#wakelockOpen
Flag: EXEMPT bug fix

Change-Id: I426fef9eda28bfa9b3405d5db2178e9eb3a527fd