Fix vulnerability that allowed attackers to start arbitary activities

Test: Flashed device and verified dream settings works as expected
Test: Installed APK from bug and verified the dream didn't allow
launching the inappropriate settings activity.
Fixes: 300090204
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:6926fd15fb16c51468dde270bd61ee68772b8c14)
Merged-In: I573040df84bf98a493b39f96c8581e4303206bac
Change-Id: I573040df84bf98a493b39f96c8581e4303206bac