Skip acquiring block-lock in BumpPointerSpace::AllocThreadUnsafe am: 6aa22c1284

Original change: https://android-review.googlesource.com/c/platform/art/+/2183095

Change-Id: I7582e6d7d4b76ca1ffc6c7dca4a45b6269298e25
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>