misc clippy fixes

the trivial ones ;)

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

proxmox-rest-server/examples/minimal-rest-server.rs

@@ -80,7 +80,7 @@ lazy_static! {
 #[api]
 /// Lists all current items
 fn list_items() -> Result<Vec<String>, Error> {
-    Ok(ITEM_MAP.lock().unwrap().keys().map(|k| k.clone()).collect())
+    Ok(ITEM_MAP.lock().unwrap().keys().cloned().collect())
 }
 
 #[api(