Add type for directories containing snapshots of apex data.

This adds a new apex_rollback_data_file type for the snapshots (backups)
of APEX data directories that can be restored in the event of a rollback.

Permission is given for apexd to create files and dirs in those directories
and for vold_prepare_subdirs to create the directories.

See go/apex-data-directories for details.

Bug: 141148175
Test: Built and flashed, checked directory was created with the correct
type.

Change-Id: I94b448dfc096e5702d3e33ace6f9df69f58340fd
diff --git a/private/vold_prepare_subdirs.te b/private/vold_prepare_subdirs.te
index 51cc138..b287bdc 100644
--- a/private/vold_prepare_subdirs.te
+++ b/private/vold_prepare_subdirs.te
@@ -15,6 +15,7 @@
 }:dir { open read write add_name remove_name rmdir relabelfrom };
 allow vold_prepare_subdirs {
     apex_module_data_file
+    apex_rollback_data_file
     backup_data_file
     face_vendor_data_file
     fingerprint_vendor_data_file
@@ -25,6 +26,7 @@
 }:dir { create_dir_perms relabelto };
 allow vold_prepare_subdirs {
     apex_module_data_file
+    apex_rollback_data_file
     backup_data_file
     face_vendor_data_file
     fingerprint_vendor_data_file