Bug Report or Feature Request (mark with an x)

- [x] bug report -> please search issues before submitting
- [ ] feature request

Command (mark with an x)

- [ ] new
- [ ] build
- [ ] serve
- [ ] test
- [ ] e2e
- [ ] generate
- [ ] add
- [x] update
- [ ] lint
- [ ] xi18n
- [ ] run
- [ ] config
- [ ] help
- [ ] version
- [ ] doc

Versions

Angular CLI: 6.2.4
Node: 10.10.0
OS: darwin x64
Angular: 6.1.9
... animations, common, compiler, compiler-cli, core, forms
... http, language-service, platform-browser
... platform-browser-dynamic, router

Package Version

@angular-devkit/architect 0.8.4
@angular-devkit/build-angular 0.8.4
@angular-devkit/build-optimizer 0.8.4
@angular-devkit/build-webpack 0.8.4
@angular-devkit/core 0.8.4
@angular-devkit/schematics 0.8.4
@angular/cli 6.2.4
@ngtools/webpack 6.2.4
@schematics/angular 0.8.4
@schematics/update 0.8.4
rxjs 6.3.3
typescript 3.1.1
webpack 4.19.1

Repro steps

 ng update --help

option --dryRun was showed 2x times

The log given by the failure

Desired functionality

should be 1x time