Fixup for matching $kernelversion on Joyent

This replaces the code that used to exist and now accommodates FreeBSD
using the $kernel fact, but still allows Joyent selection from
$kernelversion.
Add FreeBSD case for $nx_daemon_user
Add specials for FreeBSD and $root_group
Update $root_group in manifests to use platform specifics
Remove logdir selector when everything is the same
Set spec group back to original