Ticket 580 - Wrong error code return when using EXTERNAL SASL and no client certificate
Bug Description: When doing a SASL EXTERNAL bind, and no client certificate is provided,
the bind succeeds(as anonymous). However, the bind should fail with
an error 48.
Fix Description: Check for the missing client certificate and return the appropriate
Reviewed by: Noriko(Thanks!)
(cherry picked from commit 2a81336e582c68fe0326a76a2f156b469688cc9b)