Clear all timeout on destroy and close (nodejs#2535)

Signed-off-by: Matteo Collina <hello@matteocollina.com>

Author: mcollina

lib/agent.js

@@ -110,6 +110,9 @@ class Agent extends DispatcherBase {
   async [kClose] () {
     const closePromises = []
     for (const client of this[kClients].values()) {
+      if (client[kDeleteScheduled]) {
+        clearTimeout(client[kDeleteScheduled])
+      }
       closePromises.push(client.close())
     }
     this[kClients].clear()
@@ -120,6 +123,9 @@ class Agent extends DispatcherBase {
   async [kDestroy] (err) {
     const destroyPromises = []
     for (const client of this[kClients].values()) {
+      if (client[kDeleteScheduled]) {
+        clearTimeout(client[kDeleteScheduled])
+      }
       destroyPromises.push(client.destroy(err))
     }
     this[kClients].clear()