fix: unref nat manager retries

The retry operation in the NAT Manager can prevent node from shutting
down, so unref the retries so they don't keep adding work to the
event loop.

src/nat-manager.js

@@ -138,9 +138,9 @@ class NatManager {
 
     this._client = {
       // these are all network operations so add a retry
-      map: (...args) => retry(() => map(...args), { onFailedAttempt: log.error }),
+      map: (...args) => retry(() => map(...args), { onFailedAttempt: log.error, unref: true }),
-      destroy: (...args) => retry(() => destroy(...args), { onFailedAttempt: log.error }),
+      destroy: (...args) => retry(() => destroy(...args), { onFailedAttempt: log.error, unref: true }),
-      externalIp: (...args) => retry(() => externalIp(...args), { onFailedAttempt: log.error })
+      externalIp: (...args) => retry(() => externalIp(...args), { onFailedAttempt: log.error, unref: true })
     }
 
     return this._client