[ONOS-4650][ONOS-4726][ONOS-4727] [ONOS-4728]Implement must parser + when parser + feature + if-feature + revision defect fix

Change-Id: I0a3aee6c1c6b72ef7da7f7f565fd0f149fe3fd42
diff --git a/plugin/src/test/resources/LeafSubStatementMust.yang b/plugin/src/test/resources/LeafSubStatementMust.yang
new file mode 100644
index 0000000..6d7e626
--- /dev/null
+++ b/plugin/src/test/resources/LeafSubStatementMust.yang
@@ -0,0 +1,14 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    leaf ifType {
+        type enumeration {
+            enum ethernet;
+            enum atm;
+        }
+        must "ifType != 'ethernet'" {
+            description "ifType is not ethernet";
+        }
+    }
+}