Test that ensemble delete functions in yokozuna

This tests that basho/yokozuna#404 functions as planned, as well as acts as a placeholder for more ensemble yz tests. This test lives in r_t, apart from other yokozuna tests, to use the `ensemble_util` testing module. More tests are to be added.
Yeah, I add it there because it will certainly be at least 1 second, never less. It just reduces wait_until loops