fix: don't allow new connections while pool closes

This fix prevents the p2p pool from accepting or initiating new
connections while it is closing or after it has closed. This prevents
the possibility for race conditions which was affecting the Pool test
suite.

Author: sangaman

lib/p2p/Pool.ts

@@ -466,6 +466,10 @@ class Pool extends EventEmitter {
    * routine is complete
    */
   private openPeer = async (peer: Peer, expectedNodePubKey?: string, retryConnecting = false): Promise<void> => {
+    if (this.disconnecting || !this.connected) {
+      // if we are disconnected or disconnecting, don't open new connections
+      throw errors.POOL_CLOSED;
+    }
     this.bindPeer(peer);
 
     try {