The SingleReplicasStayOrMove scenario of the kudu-admin-test is a bit flaky

src/kudu/src/kudu/tools/kudu-admin-test.cc:2134: Failure
Value of: out                                                                   
Expected: has no substring "rebalancing is complete: cluster is balanced (moved 0 replicas)"
  Actual: "Per-server replica distribution summary:\n       Statistic       |  Value\n-----------------------+----------\n Minimum Replica Count | 0\n Maximum Replica Count | 0\n Average Replica Count | 0.000000\n\nPer-table replica distribution summary:\n Replica Skew | Value\n--------------+-------\n N/A          | N/A\n\n\nrebalancing is complete: cluster is balanced (moved 0 replicas)\n" (of type std::string)