ctrl: Introduce CTRL command subscriber.by-*.aud2g <algo[,ki]>

This command provides getter and setter to set and retrieve the
authentication data for 2g subscribers.

Change-Id: Ibebac232fa173bce8a075cacf477214d5bdb590f
Related: SYS#5993
diff --git a/tests/test_subscriber_errors.ctrl b/tests/test_subscriber_errors.ctrl
index 403e0fa..ac9eec7 100644
--- a/tests/test_subscriber_errors.ctrl
+++ b/tests/test_subscriber_errors.ctrl
@@ -123,3 +123,12 @@
 
 SET 53 subscriber.delete zzz
 ERROR 53 Invalid IMSI value.
+
+SET 54 subscriber.by-imsi-901990000000003.aud2g foobar
+ERROR 54 Value failed verification.
+
+SET 55 subscriber.by-imsi-901990000000003.aud2g foobar,2134
+ERROR 55 Unknown auth algorithm.
+
+SET 56 subscriber.by-imsi-901990000000003.aud2g xor,2134
+ERROR 56 Invalid KI.