Create legacy /data/system/user directory.

We create per-user directories under this location, so it should
only be created once by init, similar to all the other user-specific
directories.

Bug: 27896918
Change-Id: I9ec55e4fd763c0eda6c6e50483694a6377344586
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 3e2f0a5..28a9b9a 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -427,6 +427,7 @@
 
     mkdir /data/system 0775 system system
     mkdir /data/system/heapdump 0700 system system
+    mkdir /data/system/users 0775 system system
 
     mkdir /data/system_de 0770 system system
     mkdir /data/system_ce 0770 system system