YANG sub module linking + unsupported yang construct + defect fix

Change-Id: I224c8c14ee2111f6844278cb540c48651544f59b
diff --git a/utils/yangutils/src/test/resources/ChoiceSubStatementDefault.yang b/utils/yangutils/src/test/resources/ChoiceSubStatementDefault.yang
new file mode 100644
index 0000000..b9fd60d
--- /dev/null
+++ b/utils/yangutils/src/test/resources/ChoiceSubStatementDefault.yang
@@ -0,0 +1,23 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container food {
+       choice snack {
+           case sports-arena {
+               leaf pretzel {
+                   type string;
+               }
+               leaf beer {
+                   type string;
+               }
+           }
+           case late-night {
+               leaf chocolate {
+                   type string;
+               }
+           }
+           default "hello";
+       }
+    }
+}