Add test validating if CQL/Alternator ping works fine when REST API is unresponsive

[karol-kokoszka]

Fixes #3796 (built on top of already pending PRs)

The test fails at the current environment (EXPECTED).

    service_integration_test.go:120: Expected CQL = UP, Alternator = UP and REST != UP, but was {ERROR ERROR TIMEOUT} on {192.168.200.11}
--- FAIL: TestStatus_Ping_Independent_From_REST_Integration (37.28s)

It's gonna PASS when then whole cache-service epic is done.

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