Put shell on the idle/background whitelist

Bug 35229549

Change-Id: I9f7dd66c37af9c28c9f0714be4358b94930c2d32
diff --git a/data/etc/platform.xml b/data/etc/platform.xml
index b394c3c..344f3c8 100644
--- a/data/etc/platform.xml
+++ b/data/etc/platform.xml
@@ -179,6 +179,7 @@
 
     <!-- This is a core platform component that needs to freely run in the background -->
     <allow-in-power-save package="com.android.cellbroadcastreceiver" />
+    <allow-in-power-save package="com.android.shell" />
 
     <!-- These are the packages that are white-listed to be able to run as system user -->
     <system-user-whitelisted-app package="com.android.settings" />