clippy: Fix clippy version 0.1.60

Fix clippy lints from clippy 0.1.60 (7737e0b 2022-04-04).

Signed-off-by: Felix Obenhuber <felix@obenhuber.de>

src/systemd.rs

@@ -17,7 +17,7 @@ use crate::{ControllIdentifier, ControllerInternal, Controllers, Resources, Subs
 pub struct SystemdController {
     base: PathBuf,
     path: PathBuf,
-    v2: bool,
+    _v2: bool,
 }
 
 impl ControllerInternal for SystemdController {
@@ -66,7 +66,7 @@ impl SystemdController {
         Self {
             base: root.clone(),
             path: root,
-            v2,
+            _v2: v2,
         }
     }
 }