set handlebars as default template engine.

Author: HugoMario

modules/swagger-codegen-cli/src/main/java/io/swagger/codegen/v3/cli/cmd/Generate.java

@@ -324,10 +324,10 @@ public void run() {
             configurator.setCodegenArguments(codegenArguments);
         }
 
-        if (CodegenConstants.HANDLEBARS_TEMPLATE_ENGINE.equalsIgnoreCase(templateEngine)) {
-            additionalProperties.add(String.format("%s=%s", CodegenConstants.TEMPLATE_ENGINE, CodegenConstants.HANDLEBARS_TEMPLATE_ENGINE));
-        } else {
+        if (CodegenConstants.MUSTACHE_TEMPLATE_ENGINE.equalsIgnoreCase(templateEngine)) {
             additionalProperties.add(String.format("%s=%s", CodegenConstants.TEMPLATE_ENGINE, CodegenConstants.MUSTACHE_TEMPLATE_ENGINE));
+        } else {
+            additionalProperties.add(String.format("%s=%s", CodegenConstants.TEMPLATE_ENGINE, CodegenConstants.HANDLEBARS_TEMPLATE_ENGINE));
         }
 
         applySystemPropertiesKvpList(systemProperties, configurator);