cancelling/saving user account edits repeats action.

### Steps to reproduce
1. go to the account page once you're logged in: [account setting](https://hypothes.is/account/settings)
2. Click either cancel or save.

### Expected behaviour
The expected behaviour should be either taking you back to your profile when you click `save/cancel` or providing a way for you to edit your password/email info.

### Actual behaviour
When you click `save`, the action gets repeated indefinitely. looks like nothing happens. you keep clicking it and the page remains the same.
On the other hand, when you click `cancel`, you'd have to click it four more times before sth else happens.

### Browser/system information
Chrome, Version 63.0.3239.132
MacOs High Sierra

### Additional details

I was testing `h` and `client` when I found this. It does happen locally too, as shown in the gif.