Update test cases to be port independent

[gunjpan]

Current test cases run server on port 3000, when needed, which crashes other test cases that try to use the same port on same instance causing CI failures.
Goal is to make test server apps port independent.
Parent issue: https://github.com/strongloop-internal/scrum-loopback/issues/932

[bnoordhuis]

I'm fairly sure all tests honor the PORT environment variable.

[gunjpan]

@bnoordhuis : They do, but on our CI infrastructure, we have seen failures related to multiple builds trying to run test apps on port 3000.

[bnoordhuis]

What does "our CI" refer to? StrongLoop's? Can you link me to a failing run?

[gunjpan]

I was referring to Strongloop's CI. For the failing run, I get 404 Not found as it has been a while since the issue was created and Jenkins keeps build logs for a limited amount of time.
The initial cause was dependent builds failing with: EADDRINUSE. Will link you to the failing run when I come across one.

The end goal is to make test cases more robust. Any suggestions are appreciated.