atrace.rc: move to post-fs trigger

Test: manually
Bug: 32025203
(cherrypicked from commit 835180a675147ef7dd2a325016efd3b45523acc7)
Change-Id: I787984fc8ab7151ecce9e62a25fa03b0ecf263cd
diff --git a/cmds/atrace/atrace.rc b/cmds/atrace/atrace.rc
index e3cc9da..747cc69 100644
--- a/cmds/atrace/atrace.rc
+++ b/cmds/atrace/atrace.rc
@@ -1,6 +1,6 @@
 ## Permissions to allow system-wide tracing to the kernel trace buffer.
 ##
-on fs
+on post-fs
 
 # Allow writing to the kernel trace log.
     chmod 0222 /sys/kernel/debug/tracing/trace_marker