feat: turns on self-signed JWT feature flag (#490)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 392067151

Source-Link: googleapis/googleapis@06345f7

Source-Link: https://github.com/googleapis/googleapis-gen/commit/95882b37970e41e4cd51b22fa507cfd46dc7c4b6

src/v1/key_management_service_client.ts

@@ -145,6 +145,12 @@ export class KeyManagementServiceClient {
     // Save the auth object to the client, for use by other methods.
     this.auth = this._gaxGrpc.auth as gax.GoogleAuth;
 
+    // Set useJWTAccessWithScope on the auth object.
+    this.auth.useJWTAccessWithScope = true;
+
+    // Set defaultServicePath on the auth object.
+    this.auth.defaultServicePath = staticMembers.servicePath;
+
     // Set the default scopes in auth client if needed.
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;
@@ -4090,6 +4096,7 @@ export class KeyManagementServiceClient {
       return this.keyManagementServiceStub!.then(stub => {
         this._terminated = true;
         stub.close();
+        this.iamClient.close();
       });
     }
     return Promise.resolve();