Ticket #565 - turbo mode and replication - allow disable of turbo mode
    
    https://fedorahosted.org/389/ticket/565
    Reviewed by: mreynolds (Thanks!)
    Branch: master
    Fix Description: Add nsslapd-enable-turbo-mode configuration attribute.
    This allows the user to disable turbo mode.  The default for this setting
    is on.
    Platforms tested: RHEL6 x86_64
    Flag Day: no
    Doc impact: yes - document new config parameter