shamu: fix QXDMLogger on encrypted devices

Bug: 17044844
Change-Id: I25efda2fc92d17bd4ff2c4e582f0582549785cb7
Signed-off-by: Patrick Tjin <pattjin@google.com>
diff --git a/init.shamu.diag.rc.userdebug b/init.shamu.diag.rc.userdebug
index eaa9fe6..9836bc3 100644
--- a/init.shamu.diag.rc.userdebug
+++ b/init.shamu.diag.rc.userdebug
@@ -1,6 +1,6 @@
 # This file gets copied as /init.shamu.diag.rc
 
-on boot
+on post-fs-data
     # Modem logging collection
     mkdir /data/diag_logs 0777 system system
     chmod 666 /dev/diag