Remove unused JanusGraphMultiQueryStep when possible [tp-tests][cql-tests]

[porunov]

Fixes #3737

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[porunov]

For some reason TP tests were not executed in this PR even so I added [tp-tests] into the commit message.
Nevertheless master branch have a bug executing TP tests, thus they won't pass here anyways. See: #3747

[porunov]

I have intention of merging this PR via lazy consensus. The new behavior can be disabled if JanusGraphUnusedMultiQueryRemovalStrategy is excluded from the traversal.