Don't modify passed in apiConf

 * It prevents reuse of parsoidOptions, relevant to an upcoming patch.

Change-Id: Ic27f1e0feba0ae5c3e172d70f0b4c2d6ec079ca2

lib/config/ParsoidConfig.js

@@ -458,11 +458,14 @@ ParsoidConfig.prototype.setMwApi = function(apiConf) {
 		} else if (typeof arguments[1] === 'object') {
 			// Note that `apiConf` is aliased to `arguments[0]`.
 			prefix = arguments[0];
-			apiConf = arguments[1]; // overwrites `arguments[0]`
+			apiConf = Object.assign({}, arguments[1]);  // overwrites `arguments[0]`
 			apiConf.prefix = prefix;
 		} else {
 			apiConf = { uri: arguments[0] };
 		}
+	} else {
+		console.assert(typeof apiConf === 'object');
+		apiConf = Object.assign({}, apiConf);  // Don't modify the passed in object
 	}
 	console.assert(apiConf.uri, "Action API uri is mandatory.");
 	if (!apiConf.prefix) {