cordova plugin add --nofetch --nosave does not work

# Bug Report

## cordova plugin add flags --nosave --nofetch not working

### What is expected to happen?
no changes to android.json, ios.json, fetch.json

### What does actually happen?
plugin gets added to android.json, ios.json, fetch.json

## Information
### Command or Code
cordova plugin add ./localPlugins/someLocalPlugin/ --nosave --nofetch
### Version information
cordova-lib@9.0.1 with:
cordova-common@3.2.0
cordova-create@2.0.0
cordova-fetch@2.0.1
cordova-serve@3.0.0

Environment:
OS: darwin
Node: v10.9.0
npm: 6.2.0

## Checklist
- [x] I searched for existing GitHub issues
- [x] I updated all Cordova tooling to most recent version
- [x] I included all the necessary information above

Start by reproducing `cordova plugin add ./localPlugins/someLocalPlugin/ --nosave --nofetch` with the listed Cordova and Node versions, then trace how the `plugin add` command handles these flags. Done means the local plugin is added without changes to android.json, ios.json, or fetch.json.

Written by the indexing model from the issue text.