media utils: fix UAF in TimeCheckThread Read log tag from request list under lock to avoid use after free. Bug: 142142406 Test: make Change-Id: If4adab8c15a319dc84b7003adf3ac59a3980f075 Merged-In: If4adab8c15a319dc84b7003adf3ac59a3980f075 (cherry picked from commit 9b9b3de144ce3a145b01a01424b706f69c6d7ed6)