linearizable read concern does not check if node is still primary before it writes noop

If a stepdown occurs here, the noop write will still occur even though the node is now a secondary, leading to an inconsistent state: https://github.com/mongodb/mongo/blob/e82b201cf7d17f64f54b57f58dc9668527ab49b1/src/mongo/db/read_concern.cpp#L138-L142