Replace "flags" property with "options" with same format as fstab

Bug: 143307095
Test: Set override, check policy is as expected with sm set-virtual-disk
Change-Id: Iec31d7530b15d6d4564100816c821394e0708d53
diff --git a/FsCrypt.cpp b/FsCrypt.cpp
index f9b32a0..d1fa256 100644
--- a/FsCrypt.cpp
+++ b/FsCrypt.cpp
@@ -214,10 +214,13 @@
 
 // Retrieve the options to use for encryption policies on adoptable storage.
 static bool get_volume_file_encryption_options(EncryptionOptions* options) {
-    return ParseOptionsParts(
-            android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts"),
-            android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh"),
-            android::base::GetProperty("ro.crypto.volume.flags", "v1"), options);
+    auto contents_mode =
+            android::base::GetProperty("ro.crypto.volume.contents_mode", "aes-256-xts");
+    auto filenames_mode =
+            android::base::GetProperty("ro.crypto.volume.filenames_mode", "aes-256-heh");
+    return ParseOptions(android::base::GetProperty("ro.crypto.volume.options",
+                                                   contents_mode + ":" + filenames_mode + ":v1"),
+                        options);
 }
 
 // Install a key for use by encrypted files on the /data filesystem.