Add logging for prepare_guest

Change-Id: I2dc31acb56ee64c0c69e614a2fc96ae6b31b2ffa
diff --git a/tools/xen/prepare_guest.sh b/tools/xen/prepare_guest.sh
index 2f19b9d..77ce54a 100644
--- a/tools/xen/prepare_guest.sh
+++ b/tools/xen/prepare_guest.sh
@@ -1,5 +1,7 @@
 #!/bin/bash
 
+set -x
+
 # Configurable nuggets
 GUEST_PASSWORD=${GUEST_PASSWORD:-secrete}
 STAGING_DIR=${STAGING_DIR:-stage}