add 'rhenium' (netflow box) to site.pp

this is for:

RT #6132 - netflow collector project
RT #7290 - install OS on rhenium
RT #7368 - access for jkrauska on rhenium

I see it in DHCP and DNS but not in site.pp yet

but we need it to add Joel's account to.

it should likely also use the 'pmacct' role class

Change-Id: I66cc4457a47320dfd848a7b12ae1e0a108e91be2