oap_client_test: print test descr to stderr, check stderr

Related: OS#1592
Change-Id: If1696c8e7bfa696b250f7eac24f08f85f8f492a2
diff --git a/openbsc/tests/oap/Makefile.am b/openbsc/tests/oap/Makefile.am
index df0a43f..1bb672d 100644
--- a/openbsc/tests/oap/Makefile.am
+++ b/openbsc/tests/oap/Makefile.am
@@ -12,6 +12,7 @@
 
 EXTRA_DIST = \
 	oap_client_test.ok \
+	oap_client_test.err \
 	$(NULL)
 
 if HAVE_LIBGTP