Revert^2 "Add a holdback study for concurrent MessageQueue."

This reverts commit 7f59b19f69ea4cff4899cfb930d35ddc016a14af.

Reason for revert: Issues with devices lacking the new storage backend have been resolved, so it's safe to land early RW flag reads.

Bug: 336880969
Change-Id: Iaa94819f4b2973237ebc89523ee9bb0874c8e43d
2 files changed