// If the request has a shard version, but the operation doesn't have a shard version, this
// means it came from an old mongos instance (pre 3.2) that set the version in the "metadata"
// field instead of at the top level. Set the value in order to ensure the
// dependent code works.
// TODO(spencer): Remove this after 3.2 ships.
Improve the behaviour of multi-update/delete against a sharded collection
multiUpdate and multiRemove ops from a stale mongos may cause repeated work