Make READ_EXTERNAL_STORAGE dangerous

We have a new storage permission group that has read and
write external storage. However, read external storage is
(not a regression) a normal permission while write is a
dangerous one. This leads to cases where the user disables
the Storage permission and apps still read form it. This
change makes read external storage a dangerous permission.

bug:21949045

Change-Id: I7e28f629dda6e9c1f70cb20a3d5bea74fb109890
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index b54798b..5b40d30 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -490,7 +490,7 @@
         android:permissionGroup="android.permission-group.STORAGE"
         android:label="@string/permlab_sdcardRead"
         android:description="@string/permdesc_sdcardRead"
-        android:protectionLevel="normal" />
+        android:protectionLevel="dangerous" />
 
     <!-- Allows an application to write to external storage.
          <p class="note"><strong>Note:</strong> If <em>both</em> your <a