(maint) Update dev postinst to use @etc_dir
(maint) Update dev postinst to use @etc_dir

This replaces instances of @config_dir/.. with the equivalent @etc_dir
invocation to be more readable.

shrug/puppetdb,kbrezina/puppetdb,shrug/puppetdb,ajroetker/puppetdb,grimradical/puppetdb,rbrw/puppetdb,mullr/puppetdb,wkalt/puppetdb,highb/puppetdb,puppetlabs/puppetdb,jantman/puppetdb,waynr/puppetdb,puppetlabs/puppetdb,ajroetker/puppetdb,ajroetker/puppetdb,waynr/puppetdb,wkalt/puppetdb,highb/puppetdb,kbrezina/puppetdb,johnduarte/puppetdb,melissa/puppetdb,ajroetker/puppetdb,shrug/puppetdb,puppetlabs/puppetdb,rbrw/puppetdb,highb/puppetdb,kbarber/puppetdb,wkalt/puppetdb,mullr/puppetdb,johnduarte/puppetdb,waynr/puppetdb,mullr/puppetdb,wkalt/puppetdb,waynr/puppetdb,puppetlabs/puppetdb,cprice404/puppetdb,johnduarte/puppetdb,kbarber/puppetdb,kbarber/puppetdb,kbrezina/puppetdb,mullr/puppetdb,melissa/puppetdb,senior/puppetdb,melissa/puppetdb,johnduarte/puppetdb,puppetlabs/puppetdb,jantman/puppetdb,senior/puppetdb,rbrw/puppetdb,grimradical/puppetdb,rbrw/puppetdb,shrug/puppetdb,highb/puppetdb,senior/puppetdb,senior/puppetdb,grimradical/puppetdb,cprice404/puppetdb,grimradical/puppetdb,mullr/puppetdb,jantman/puppetdb,rbrw/puppetdb,kbrezina/puppetdb,cprice404/puppetdb,kbarber/puppetdb