Allow vold to get the DSU status

Currently, the vold detects the factory reset by checking the
metadata encryption key. This logic is only valid when the
device is not in DSU mode. This CL allows vold to get the DSU
status.

Test: run DSU installation on a Pixel device
Bug: 199222795
Change-Id: Ia6ca3b27afd52347b132d7e2d8be244fb9f15e7d
diff --git a/private/vold.te b/private/vold.te
index de0fde4..1ad1f43 100644
--- a/private/vold.te
+++ b/private/vold.te
@@ -22,6 +22,7 @@
 get_prop(vold, vold_config_prop)
 get_prop(vold, storage_config_prop);
 get_prop(vold, incremental_prop);
+get_prop(vold, gsid_prop);
 
 set_prop(vold, vold_post_fs_data_prop)
 set_prop(vold, vold_prop)