Ticket 48665 - Fix RHEL6 test compatibility issues
    
    Bug description: It is impossible to use inst.whoami_s() on RHEL6.
    It throws PROTOCOL_ERROR: 'unsupported extended operation'.
    
    Fix description: Use a search to verify that the server has not
    crushed.
    
    https://fedorahosted.org/389/ticket/48665
    
    Reviewed by: nhosoi (Thanks!)