debugger: fix event listener leak in the run command

It should remove both the error and the ready event listeners
attached when either of them fires, instead of removing only
the one whose corresponding event fires, otherwise the other
event listener will always get leaked.

Author: joyeecheung

lib/internal/debugger/inspect_client.js

@@ -344,8 +344,20 @@ class Client extends EventEmitter {
     };
 
     return new Promise((resolve, reject) => {
-      this.once('error', reject);
-      this.once('ready', resolve);
+      const tearDown = () => {
+        this.removeListener('ready', onReady);
+        this.removeListener('error', onError);
+      };
+      const onError = (err) => {
+        tearDown();
+        reject(err);
+      };
+      const onReady = () => {
+        tearDown();
+        resolve();
+      };
+      this.once('error', onError);
+      this.once('ready', onReady);
 
       httpReq.on('upgrade', handshakeListener);
       httpReq.end();

test/common/debugger.js

@@ -141,6 +141,10 @@ function startCLI(args, flags = [], spawnOpts = {}, opts = { randomPort: true })
       return getOutput();
     },
 
+    get stderrOutput() {
+      return stderrOutput;
+    },
+
     get rawOutput() {
       return outputBuffer.join('').toString();
     },

test/parallel/test-debugger-restart-message.js

@@ -31,6 +31,8 @@ const startCLI = require('../common/debugger');
     } finally {
       await cli.quit();
     }
+
+    assert.doesNotMatch(cli.stderrOutput, /MaxListenersExceededWarning/);
   }
 
   onWaitForInitialBreak();