tweak ps4 for readability

After staring at a bunch of logs, try to crisp up the ps4 output for
maximum readability.

This also adds PS4 to all calling scripts by having a common PS4 in
stackrc. It should make understanding when clean fails a bit more
straight forward.

Change-Id: Ia1f8dff5c1102c32c146a020a9f033c65d2c50de
diff --git a/unstack.sh b/unstack.sh
index 8eded83..47beb04 100755
--- a/unstack.sh
+++ b/unstack.sh
@@ -87,6 +87,8 @@
 # ``os_RELEASE``, ``os_UPDATE``, ``os_PACKAGE``, ``os_CODENAME``
 GetOSVersion
 
+set -o xtrace
+
 # Run extras
 # ==========