Ticket 47840 - add configure option to disable instance specific scripts
    https://fedorahosted.org/389/ticket/47840
    
    Bug Description:  Now that ​https://fedorahosted.org/389/ticket/528 is
    fixed, the next step is to allow building the server with the instance specific
    scripts disabled.
    
    Fix Description:  Instead of defining a configure option, we provide a new
    option in setup-ds.pl, slapd.InstScriptsEnabled, which defaults to false. All
    new installs of 389 will NOT install with a inst_dir nor the scripts that are in
    that directory.
    
    Additionally, this change fixes setup-ds.pl to correctly use the sbindir scripts
    to start/stop the server instance during installation.
    
    Finally, we add support for setup-ds.pl so that in --update if the inst_dir
    exists, scripts will be updated, but if it does not exist, no action is taken.
    
    In time, we will alter --update to *remove* the scripts within inst_dir during
    the update (We have no way of knowing if a customer has put custom scripts in
    inst_dir)
    
    Example:
    /opt/dirsrv/sbin/setup-ds.pl slapd.InstScriptsEnabled=false
    
    Author: wibrown
    
    Review by: nhosoi (Thanks!)