Remove resources.apk from ZipSet when removing overlay

When a theme that is currently applied is updated, the resources.apk
prior to the update remains in the AssetManager ZipSet and is still
used when loading themed assets.  This patch removes the resources.apk
from the ZipSet so that the new one can be correctly loaded in.

Change-Id: Ia0b415a3598779825090f365581d374bf51c812d
REF: THEMES-639
(cherry picked from commit 59c97bd8)