Stop passing in statsFile fds as they will be leaked when returned to the caller.

This is safe, as getCommittedStatsMerged() supports null-able values for the List<ParcelFileDescriptor>.

Test: local compile and test; atom still pulls successfully.
Change-Id: I083ea1150f54c5970fbf60ae320809d27c4f3207
Merged-In: I083ea1150f54c5970fbf60ae320809d27c4f3207
Bug: 179008261
(cherry picked from commit e451771a)