feat(testlab): set port to zero in givenHttpServerConfig

[bajtos]

Modify the test helper givenHttpServerConfig to explicitly set the port to zero. With this change in place, applications can use this helper in acceptation tests without having to explicitly specify {port: 0} to override RestServer's default port 3000.

Checklist

• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

[bajtos]

AppVeyor's failure is unrelated to these changes.

123 1) build
124       generates apidocs:
125     Error: Timeout of 30000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (C:\projects\loopback-next\packages\build\test\integration\scripts.integration.js)
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