Test ber encoding of message_id > 128

@mtodd I'm not sure if there was an issue filed for this, but you mentioned there was a BER encoding issue for message ID's greater than 128. I expected this integration test against OpenLDAP to fail, but it does not. I double checked the same Connection is being reused, and that the message ID is incrementing. Was there other factors I missed?
TBQH, the reference doc isn't actually all that helpful for the implementation, at least from my experience. But vital to point others (and future selves) to the right place.