Expand nuplayer mutex for mediametrics management

refactor some mutex for how nuplayer sets up mediametrics data.
expanded locking to eliminate a couple race conditions.

Bug: 151644303
Bug: 151643722
Test: poc attached to bugs
Merged-In: I75f29a6254c5eab5d4f524ee7a7ef59f93a0b405
Merged-In: Ia2e68ef616e249a6e8746b9068f22bd208a0ffc8
Change-Id: I1e9bbcd67a1510f70fad66e8ef77f529008e248a
(cherry picked from commit 86b46a20b2730790759aefcfa4c5d0cb3589c61b)
2 files changed