fix: do not set path to plugin config defined as a Function or an Array

If a plugin hook was defined as a `Function` or an `Array` the `path` property would be set to the default value.
Even if this bug had no actual negative impact, it should be fixed so the code would perform as intended.

lib/plugins/index.js

@@ -1,4 +1,4 @@
-const {isArray, isObject, omit, castArray, isUndefined} = require('lodash');
+const {isPlainObject, omit, castArray, isUndefined} = require('lodash');
 const AggregateError = require('aggregate-error');
 const getError = require('../get-error');
 const PLUGINS_DEFINITIONS = require('../definitions/plugins');
@@ -15,7 +15,7 @@ module.exports = (options, pluginsPath, logger) => {
       pluginConfs = def;
     } else {
       // If an object is passed and the path is missing, set the default one for single plugins
-      if (isObject(options[pluginType]) && !options[pluginType].path && !isArray(def)) {
+      if (isPlainObject(options[pluginType]) && !options[pluginType].path && castArray(def).length === 1) {
         options[pluginType].path = def;
       }
       if (config && !config.validator(options[pluginType])) {