Fix for moleculer 0.14

[sampaiodiego]

$node.services response has no nodes property by default, so I've added grouping: true param to still receive it.

btw looks like test don't cover this change. let me know what else I can do.

[coveralls]

Pull Request Test Coverage Report for Build 116

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.468%

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Totals
Change from base Build 103:	0.0%
Covered Lines:	299
Relevant Lines:	308

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💛 - Coveralls