Ticket 47416 - SASL encrypted packet length exceeds maximum allowed limit
    
    Bug Description:  If an error occurs while establishing the secure layer during
                      a bind operation, the client will send an unbind request that
                      is not encrypted.  The sasl code expects encrypted values
                      and it incorrectly parses the message for its length, but since
                      it's not encrypted the length is wrong, and exceeds the saslio limit.
    
    Fix Description:  Check if there is data in the encrypted buffer before the secure
                      layer is established.  Check if the first byte in the buffer is an
                      LDAP_TAG_MESSAGE.  Then we get the legnth of the LDAP message, and compare
                      it to maxbersize.  Then attmept to read in the rest of the
                      packet(if necessary).  If we fail to read in the LDAP msg length,
                      then return PR_WOULD_BLOCK_ERROR.  Otherwise parse the berElement, and
                      check if it is an UNBIND operation.  If it is then copy it to the socket
                      buffer, and let the server process the operation.  Any other valid
                      LDAP operation is still treated as an error.
    
    https://fedorahosted.org/389/ticket/47416
    
    Reviewed by: richm (Thanks!!!)