Unhibernate an app when a user exempts it

When an app is exempted from hibernation, we unhibernate as well. This
prevents confusing situations where a user may return to the "Unused
Apps" page and sees that the app is still there even after exemption.

Bug: 205641871
Test: untoggle "Remove permissions and free up space". See app is
removed from "Unused Apps"

Merged-In: I205d2f3a53d3b111f8d34b2857f76b0efee26844
Change-Id: I205d2f3a53d3b111f8d34b2857f76b0efee26844