tests: only check IU configs if IU is enabled

Fix vty tests that are failing since libosmocore change
Ic225232fbfca49ba868427eaf898e1f6e34e1ca8. If OsmoMSC is built without
IU support, it fails with "cs7-instance-iu" in the config.

Change-Id: Ie56da9167badfd2399b566af91a345103f46c2a1
diff --git a/osmoappdesc.py b/osmoappdesc.py
index 886c682..bd7fea3 100644
--- a/osmoappdesc.py
+++ b/osmoappdesc.py
@@ -14,13 +14,16 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>
 
+import os
+
 app_configs = {
-    "msc": ["doc/examples/osmo-msc/osmo-msc.cfg",
-            "doc/examples/osmo-msc/osmo-msc_custom-sccp.cfg",
-            "doc/examples/osmo-msc/osmo-msc_multi-cs7.cfg",
-	   ],
+    "msc": ["doc/examples/osmo-msc/osmo-msc.cfg"],
 }
 
+if os.environ["IU"] == "1":
+    app_configs["msc"] += ["doc/examples/osmo-msc/osmo-msc_custom-sccp.cfg",
+                           "doc/examples/osmo-msc/osmo-msc_multi-cs7.cfg"]
+
 apps = [(4254, "src/osmo-msc/osmo-msc", "OsmoMSC", "msc"),
         ]