Don't try to fixate CE keys for ephemeral users

Ephemeral users don't have keys stored on disk at all, so it's neither
necessary nor possible to manipulate the disk keys here.

Bug: 30038313
Change-Id: Idc7ec1bfe1e8a6ffa6cee2f284dbe378097b08da
diff --git a/Ext4Crypt.cpp b/Ext4Crypt.cpp
index 7d65364..cb41295 100644
--- a/Ext4Crypt.cpp
+++ b/Ext4Crypt.cpp
@@ -614,6 +614,7 @@
 bool e4crypt_fixate_newest_user_key_auth(userid_t user_id) {
     LOG(DEBUG) << "e4crypt_fixate_newest_user_key_auth " << user_id;
     if (!e4crypt_is_native()) return true;
+    if (s_ephemeral_users.count(user_id) != 0) return true;
     auto const directory_path = get_ce_key_directory_path(user_id);
     auto const paths = get_ce_key_paths(directory_path);
     if (paths.empty()) {