Handle Splunk forwarder upgrades when going to version 9

[treydock]

Without this the upgrade from v8 to v9 forwarder would timeout on the stop command as it ends up forwarding start/stop to systemd so the start will actually start the service with v9.

[treydock]

Upgrading Forwarder from 8.0.x to 9.0.4:

[root@grafana-test ~]# puppet agent -t
Info: Using environment 'test'
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Loading facts
Info: Caching catalog for grafana-test.OMIT
Info: Applying configuration version '1680616232'
Notice: /Stage[main]/Splunk::Forwarder::Install/Package[splunkforwarder]/ensure: ensure changed '8.2.6-a6fe1ee8894b' to '9.0.4-de405f4a7979'
Info: /Stage[main]/Splunk::Forwarder::Install/Package[splunkforwarder]: Scheduling refresh of Exec[splunk-forwarder-accept-tos]
Notice: /Stage[main]/Splunk::Forwarder::Service::Nix/Exec[splunk-forwarder-accept-tos]: Triggered 'refresh' from 1 event
Notice: /Stage[main]/Splunk::Forwarder::Service/Service[SplunkForwarder]/enable: enable changed 'false' to 'true' (corrective)
Notice: Applied catalog in 90.49 seconds

[aimaard]

@treydock The GitHub actions are fixed, feel free to rebase onto master, then your tests should pass and we can get this merged.