test: gprs_ns2: free the nsi after each test

Change-Id: I700da48d7afe6b1a81484a0725faf0c56073446d
diff --git a/tests/gb/gprs_ns2_test.c b/tests/gb/gprs_ns2_test.c
index 4c47b6a..bcfd460 100644
--- a/tests/gb/gprs_ns2_test.c
+++ b/tests/gb/gprs_ns2_test.c
@@ -142,6 +142,7 @@
 	ns2_nse_notify_unblocked(nsvc[1], false);
 	OSMO_ASSERT(ns2_count_transfer_cap(nse, 0) == 42 + 23);
 
+	gprs_ns2_free(nsi);
 	printf("--- Finish NSE transfer cap\n");
 
 }