New user is not cleared after adding

[rickr]

When adding a user After the user is successfully added The input box is not cleared. It should clear after a successful addition of a user.

Steps to rep:

1. Visit /admin/users
2. Click the + to add a user
3. Add a user called "test"
4. The user should appear in the user list, the dialog box should close.
5. Click the + to add another user
6. The previous user ("test") is still present