Wifi: Fix Wifi Multicast Wakelock Statistics

In current implementation, when the same UID holds multiple WiFi
wakelocks, the timer for the lock acquisition in batterystats is started
with the first wakelock acquire and stops with first release.
So the nesting of wakelocks of the same Uid is not correctly accounted for.
(so if Lock#1 acquired at T1, Lock# 2 acquired at T2, Lock#2 released at T3,
lock #1 released at T4 , the timer will only consider the interval T3 - T1 which
is not the correct value).

This commit fixes this issue by starting the timer on the first
acquisition, and stopping it on the last release

Bug: 70691435
Test: Unit Test
Test: $ atest BatteryStatsImplTest

Change-Id: Ie955b6ab0eb1e9837fdda2b8d81835038b8d71da