init: add missing O_CLOEXEC

Test: (hopefully) no more denials at boot
Change-Id: I7c20a9bbf27210e0ee5f1bbe69db36bb47c38892
diff --git a/init/persistent_properties.cpp b/init/persistent_properties.cpp
index 3b5a41d..1758cfa 100644
--- a/init/persistent_properties.cpp
+++ b/init/persistent_properties.cpp
@@ -198,7 +198,7 @@
     // Note in this case, that the source and destination directories are the same, so only one
     // fsync() is required.
     auto dir = Dirname(persistent_property_filename);
-    auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY | O_RDONLY)};
+    auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY | O_RDONLY | O_CLOEXEC)};
     if (dir_fd < 0) {
         return ErrnoError() << "Unable to open persistent properties directory for fsync()";
     }