sgsn/test: Add test_gmm_attach

This test checks the attach procedure until the Attach Complete is
received.

Note that authorization and GMM state updates are not working
properly yet.

Sponsored-by: On-Waves ehf
diff --git a/openbsc/tests/sgsn/sgsn_test.ok b/openbsc/tests/sgsn/sgsn_test.ok
index ea5b0fa..c03bb1e 100644
--- a/openbsc/tests/sgsn/sgsn_test.ok
+++ b/openbsc/tests/sgsn/sgsn_test.ok
@@ -3,4 +3,5 @@
 Testing GMM detach (power off)
 Testing GMM detach (no MMCTX)
 Testing GMM Status (no MMCTX)
+Testing GMM attach
 Done