systemctl: Use relative path

[bastelfreak]

replacement of #135. it's not required to provide an absolute path. I tested this on debian and centos, works fine.

Info: /Stage[main]/Nftables::Inet_filter/Nftables::Chain[INPUT]/File[/etc/nftables/puppet/inet-filter-chain-INPUT.nft]: Scheduling refresh of Service[nftables]
Debug: /Stage[main]/Nftables::Inet_filter/Nftables::Chain[INPUT]/File[/etc/nftables/puppet/inet-filter-chain-INPUT.nft]: The container Nftables::Chain[INPUT] will propagate my refresh event
Debug: Nftables::Chain[INPUT]: The container Class[Nftables::Inet_filter] will propagate my refresh event
Debug: Executing: '/bin/systemctl is-active -- nftables'
Debug: Executing: '/bin/systemctl is-enabled -- nftables'
Debug: Executing: '/bin/systemctl is-active -- nftables'
Debug: Executing: '/bin/systemctl show --property=NeedDaemonReload -- nftables'
Debug: Executing: 'systemctl reload nftables'
Notice: /Service[nftables]: Triggered 'refresh' from 1 event