Grant shell REBOOT permission

Shell already can reboot a device (via `adb reboot` command). This
change allows shell to also trigger a reboot logic inside the
system_server.

Additionally, it allows to CTS test PowerManager.reboot API.

Test: adb shell svc reboot
Change-Id: I4545c4f3587fee2840a00648c569f75bb57501fc
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index 84d9bb6..a57377e 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -91,6 +91,7 @@
     <uses-permission android:name="android.permission.TEST_MANAGE_ROLLBACKS" />
     <uses-permission android:name="android.permission.ACCESS_SURFACE_FLINGER" />
     <uses-permission android:name="android.permission.READ_FRAME_BUFFER" />
+    <uses-permission android:name="android.permission.REBOOT" />
     <uses-permission android:name="android.permission.DEVICE_POWER" />
     <uses-permission android:name="android.permission.POWER_SAVER" />
     <uses-permission android:name="android.permission.INSTALL_LOCATION_PROVIDER" />