Replace usage of base::Callback with std::function am: 2f6c25ae86

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2647744

Change-Id: I659ffb6b205e09c2559548b13bef15e575498471
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>