Add initial sepolicy for app data snapshots.

Define a rollback_data_file label and apply it to the snapshots
directory. This change contains just enough detail to allow
vold_prepare_subdirs to prepare these directories correctly.

A follow up change will flesh out the access policy on these
directories in more detail.

Test: make, manual
Bug: 112431924

Change-Id: I4fa7187d9558697016af4918df6e34aac1957176
diff --git a/private/vold_prepare_subdirs.te b/private/vold_prepare_subdirs.te
index e93e1e5..09d0ca9 100644
--- a/private/vold_prepare_subdirs.te
+++ b/private/vold_prepare_subdirs.te
@@ -17,6 +17,7 @@
     face_vendor_data_file
     fingerprint_vendor_data_file
     iris_vendor_data_file
+    rollback_data_file
     storaged_data_file
     vold_data_file
 }:dir { create_dir_perms relabelto };
@@ -24,6 +25,7 @@
     face_vendor_data_file
     fingerprint_vendor_data_file
     iris_vendor_data_file
+    rollback_data_file
     storaged_data_file
     system_data_file
     vold_data_file