Clear WifiUsabilityStatsEntry while reusing it

The WifiUsabilityStatsEntry removed from ring buffer is not clear, it's
possible some stale data will be passed into new WifiUsabilityStatsEntry.

Flag: EXEMPT, bug fix
Bug: 377723852
Test: atest; on device test
Change-Id: I053228b9ca81041029505ccfd28c40b941170b8c
1 file changed