Changes in how faces from themes are applied in 24.1?

[Nikolai Weibull]

Hi!

In 23.4, faces specified for themes would override any set before the
theme was applied.  I upgraded to 24.1 an hour ago and now I get a
merged result of what I specify in the theme and what the face is set
to before/after the theme was/is loaded.  For example, I’ve set
font-lock-variable-name-face to (:inherit default), but it also gets a
foreground of LightGoldenrod (the default as defined in font-lock.el).

How do I get the previous behavior, where the face only had the
properties listed in the specification to custom-theme-set-faces?