Revert "use nonblockinghashmap so server does not drop transaction tokens in the face of high concurrency"

This reverts commit f377c1356274bcfb180b3e7974cc6605800333f3.
Revert "Switch to using guava caches with weak references alongside"

This reverts commit 28d4f7f326e8e2f46f7a3f72176b92069653dbc5.
Revert "fix flaky test"

This reverts commit c9e473387057c4760228264875cd061b599db61e.