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/eth2_libp2p/src/peer_manager/peer_info.rs

@@ -97,7 +97,7 @@ impl<T: EthSpec> PeerInfo<T> {
     }
 
     /// Returns the seen IP addresses of the peer.
-    pub fn seen_addresses<'a>(&'a self) -> impl Iterator<Item = IpAddr> + 'a {
+    pub fn seen_addresses(&self) -> impl Iterator<Item = IpAddr> + '_ {
         self.seen_addresses
             .iter()
             .map(|socket_addr| socket_addr.ip())