This commit ensures that check-mode works on systems when this role is
run without any telegraf being installed.
Before
```
fatal: [host-1]: FAILED! => {"changed": false, "msg": "Could not find the requested service telegraf: host"}
```
After
```
fatal: [host-1]: FAILED! => {"changed": false, "msg": "Could not find the requested service telegraf: host"}
...ignoring
```
