[ONOS-5884]YANG Serializer: Implement XML serializer.

Change-Id: Idffda88938d9c6c7b7c7814127a340bd2dc35039
diff --git a/serializers/xml/src/test/resources/testContainer.xml b/serializers/xml/src/test/resources/testContainer.xml
new file mode 100644
index 0000000..ee679b8
--- /dev/null
+++ b/serializers/xml/src/test/resources/testContainer.xml
@@ -0,0 +1,8 @@
+<food xmlns="yrt:food">
+<p1>p1_value</p1>
+<p2>p2_value</p2>
+<p2>p2_value1</p2>
+</food>
+<c2 xmlns="yrt:food">
+<p3>p3_value</p3>
+</c2>
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