Ticket #47320 - put conn on work_q not poll list if conn has buffered more_data
    
    Description: Additional change to
      commit ed88c40218c3fb8944618927e7865d74bc922c02
    to fix the self-deadlock.
    Replacing bind_credentials_set with bind_credentials_set_nolock
    in handle_handshake_done.  The handle_handshake_done is only
    called from connection_read_operation, where lock on c_mutex
    is already obtained.  Thus, the replacement is safe.
    
    https://fedorahosted.org/389/ticket/47320