fix test_subscriber_errors.ctrl after libosmocore change

libosmocore Ie35a02555b76913bb12734a76fc40fde7ffb244d
"ctrl: on parse errors, return a detailed message to sender"
the test_subscriber_errors.ctrl test fails.

Adjust the expected error message.

Change-Id: I3aee1507721cd073f72369150d0fb3cff0fdf66f
diff --git a/tests/test_subscriber_errors.ctrl b/tests/test_subscriber_errors.ctrl
index 2f64fdb..55c7480 100644
--- a/tests/test_subscriber_errors.ctrl
+++ b/tests/test_subscriber_errors.ctrl
@@ -97,9 +97,9 @@
 ERROR 43 Value failed verification.
 
 SET 44 subscriber.by-imsi-901990000000001.ps-enabled
-ERROR err Command parser error.
+ERROR 44 SET incomplete
 SET 45 subscriber.by-imsi-901990000000001.cs-enabled
-ERROR err Command parser error.
+ERROR 45 SET incomplete
 
 GET 46 subscriber.by-imsi-1234567890123456.ps-enabled
 ERROR 46 Invalid value part of 'by-xxx-value' selector.