Clippy 1.49.0 updates and dht persistence test fix (#2156)

## Issue Addressed

`test_dht_persistence` failing

## Proposed Changes

Bind `NetworkService::start` to an underscore prefixed variable rather than `_`.  `_` was causing it to be dropped immediately

This was failing 5/100 times before this update, but I haven't been able to get it to fail after updating it

Co-authored-by: realbigsean <seananderson33@gmail.com>

beacon_node/network/src/sync/range_sync/chain.rs

@@ -161,7 +161,7 @@ impl<T: BeaconChainTypes> SyncingChain<T> {
     }
 
     /// Peers currently syncing this chain.
-    pub fn peers<'a>(&'a self) -> impl Iterator<Item = PeerId> + 'a {
+    pub fn peers(&self) -> impl Iterator<Item = PeerId> + '_ {
         self.peers.keys().cloned()
     }