Only fail GetBag if there was an IO Error

AssetManager2::GetBag* functions may return "no value" for
the missing resources, that's not an error and shouldn't
result in java exceptions

+ fix the perf regression from extra level of indirection

Bug: 282264161
Test: libandroidfw_tests + boot
Change-Id: Iea32b248b1ca9f6a366b44a14866da16d6b2ef6b
2 files changed