vold now prepares a subdirectory for face data.

Change-Id: I32ec05942aac03b95b2abe5d042833197d69706b
Fixes: 116528212
Test: Built and tested locally.
diff --git a/vold_prepare_subdirs.cpp b/vold_prepare_subdirs.cpp
index 8c3df30..b8e5cb6 100644
--- a/vold_prepare_subdirs.cpp
+++ b/vold_prepare_subdirs.cpp
@@ -133,6 +133,10 @@
             if (!prepare_dir(sehandle, 0700, AID_SYSTEM, AID_SYSTEM, vendor_de_path + "/fpdata")) {
                 return false;
             }
+            auto facedata_path = vendor_de_path + "/facedata";
+            if (!prepare_dir(sehandle, 0700, AID_SYSTEM, AID_SYSTEM, facedata_path)) {
+                return false;
+            }
         }
         if (flags & android::os::IVold::STORAGE_FLAG_CE) {
             auto misc_ce_path = android::vold::BuildDataMiscCePath(user_id);