Unnecessary prompt for available port in react-native

[96f3e4c]

Describe the bug
When using storybook with react-native, yarn storybook which runs start-storybook -p 7007 prompting

Port 7007 is not available. Would you like to run Storybook on port 7007 instead?

To Reproduce
Steps to reproduce the behavior:

npx react-native init myapp
cd myapp
npx -p @storybook/cli sb init

 • Detecting project type. ✓
? Do you want to install dependencies necessary to run storybook server? You can manually do it later by install @storybook/react-native-server
Yes
...
yarn storybook

Expected behavior
If the specified port(ie: using the option -p for start-storybook) is available it should run without any prompt

Screenshots

System:

    @storybook/addon-actions: ^5.2.4 => 5.2.4 
    @storybook/addon-links: ^5.2.4 => 5.2.4 
    @storybook/addons: ^5.2.4 => 5.2.4 
    @storybook/react-native: ^5.2.4 => 5.2.4 
    @storybook/react-native-server: ^5.2.4 => 5.2.4

[shilman]

Yay!! I just released https://github.com/storybookjs/storybook/releases/tag/v5.2.5 containing PR #8491 that references this issue. Upgrade today to try it out!

[shilman]

Ermahgerd!! I just released https://github.com/storybookjs/storybook/releases/tag/v5.3.0-alpha.24 containing PR #8491 that references this issue. Upgrade today to try it out!

You can find this prerelease on the @next NPM tag.

[shilman]

Huzzah!! I just released https://github.com/storybookjs/storybook/releases/tag/v5.3.0-alpha.32 containing PR #8584 that references this issue. Upgrade today to try it out!

You can find this prerelease on the @next NPM tag.

[shilman]

Boo-yah!! I just released https://github.com/storybookjs/storybook/releases/tag/v5.2.6 containing PR #8584 that references this issue. Upgrade today to try it out!