[TEST] Stabelize MoreLikeThisActionTests

The `testCompareMoreLikeThisDSLWithAPI` test compares results from query
and API which might query different shards. Those shares might use
different doc IDs internally to disambiguate. This commit resorts the
results and compares them after stable disambiguation.
[TEST] Beef up MoreLikeThisActionTests#testCompareMoreLikeThisDSLWithAPI