Writing an oplog entry for prepare should not push the lastApplied timestamp

commit: 8c5002b06fd737f75941a73785ce75e3ca7f5ce1 1. Put a 5 second sleep between (1) and (2) to increase the chance that another transaction starts in between. opObserver->onTransactionPrepare(opCtx); lk.lock(); _checkIsActiveTransaction(lk, *opCtx->getTxnNumber(), true); invariant(_txnState == MultiDocumentTransactionState::kPrepared); + sleep(5); opCtx->getWriteUnitOfWork()->prepare(); 2. repro.js: const session = db.getMongo().startSession({causalConsistency: false}); const sessionDB = session.getDatabase('test'); sessionDB.a.insert({x: 1}); session.startTransaction({readConcern: {level: "snapshot"}}); assert.commandWorked(sessionDB.runCommand({ update: 'a', updates: [{q: {x: 1}, u: {$inc: {x: 1}}}], })); let awaitShell = startParallelShell(function() { const session = db.getMongo().startSession({causalConsistency: false}); const sessionDB = session.getDatabase('test'); while (1) { session.startTransaction({readConcern: {level: "snapshot"}}); sessionDB.a.find().toArray(); session.abortTransaction(); } }); assert.commandWorked(sessionDB.adminCommand({prepareTransaction: 1})); session.abortTransaction(); awaitShell();