Add external_storage properties.

Since these need to be set from a vendor context.

Bug: 152170470
Bug: 153525566
Test: N/A
Change-Id: I2e90ad08fa0a5bd2b4759d92f95d35cec2b316df
diff --git a/private/vold.te b/private/vold.te
index 3210779..3332d63 100644
--- a/private/vold.te
+++ b/private/vold.te
@@ -20,6 +20,7 @@
 
 # Property Service
 get_prop(vold, vold_config_prop)
+get_prop(vold, storage_config_prop);
 
 set_prop(vold, vold_prop)
 set_prop(vold, vold_status_prop)