tweak example config

Remove 'logging level all' setting.
Tweak some more logging details (to my current favorite).

Add USSD example for showing the IMSI.

Change-Id: I8296832704d779df5f1b20a595b568c99780e64d
diff --git a/tests/test_nodes.vty b/tests/test_nodes.vty
index d2c455f..95e132d 100644
--- a/tests/test_nodes.vty
+++ b/tests/test_nodes.vty
@@ -117,4 +117,5 @@
  gsup
   bind ip 127.0.0.1
  ussd route prefix *#100# internal own-msisdn
+ ussd route prefix *#101# internal own-imsi
 end