Change password instead of choose password

[Leo Arias]

On my account page (after logging in at https://login.ubuntu.com/), I can change my password. But it's not clear, because the label says "Choose password". At first, I though that it was asking me for a new password, so I almost change it without wanting it.

The label should be "Change password". This would require to make a different widget for the register and edit cases, but anyway this is required because it's also missing the field to enter the old password, as reported in bug #805499