fix [#582] - resolving random HMR port - better solution

[r3stm4n]

Summary
Port from cli/options can be string, so parseInt is required.
Two cases (--port 23300):

1. if port is already taken then without parseInt resolvePort will return 230001 (should be 23001)
2. if port is string HMR port will be 230001 (should be 23001)

Please revert previous merge #586
This is better solution.

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[ulivz]

LGTM