8261: Use test flag to skip JDP multicast tests in JolokiaTest

[skarsaune]

I just became aware that there is a new flag used to skip JDP tests. I previously added some env checking to skip similar multicast tests for Jolokia. Hence it would be a lot cleaner to use the new standardized mechanism for this. Trying out whether this fixes JMC-8261

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Progress

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Issue

• JMC-8261: Use test flag to skip JDP multicast tests in JolokiaTest (Enhancement - P5)

Reviewing

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$ git pr checkout 588

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