Add junos_config unit test (#24005)

test/units/modules/network/junos/fixtures/junos_config.json

@@ -0,0 +1,28 @@
+
+{
+    "interfaces" : [
+    {
+        "interface" : [
+        {
+            "name" :
+            {
+                "data" : "ae11"
+            },
+            "unit" : [
+            {
+                "name" :
+                {
+                    "data" : "0"
+                },
+                "description" : [
+                {
+                    "data" : "Test"
+                }
+                ]
+            }
+            ]
+        }
+        ]
+    }
+    ]
+}