init.rc: use oom_score_adj instead of oom_adj

Use kernel oom_score_adj interface to make init and children unkillable.

Stop using older, deprecated oom_adj interface.

Use OOM_SCORE_ADJ_MIN to make the processes unkillable (previously the processes
were set to a very low score, but not unkillable).

Change-Id: I680965009585c2a5a580859fb946f2d0caa95d9c
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 27acc9d..d39dd0a 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -11,7 +11,7 @@
 
 on early-init
     # Set init and its forked children's oom_adj.
-    write /proc/1/oom_adj -16
+    write /proc/1/oom_score_adj -1000
 
     # Set the security context for the init process.
     # This should occur before anything else (e.g. ueventd) is started.