Allow LoginException output to be sent in LOGIN_FAILED message to client

A LOGIN_FAILURE protocol message includes a reason why the login failed. Currently, if login fails for any reason, the reason included in the LOGIN_FAILURE message is fixed and cannot be configured ("Login refused"). A member of the community would like, in the case of an authentication failure, for the LoginException to be included in the reason field of the LOGIN_FAILURE protocol message that is sent back to the client. Perhaps this capability can be controlled with a system property.