Fixes and updates for repl_consistent_object_filter test

The `repl_consistent_object_filter` test is failing when trying to setup the clusters for testing due to an outdated use of `buckets.default.siblings` for setting `allow_mult` to `false`. An example of such a failure is [here](http://giddyup.basho.com/#/projects/riak_ee/scorecards/96/96-2133-repl_consistent_object_filter-centos-6-64/47753/artifacts/767410).

This usage needs to be updated so the test will pass.

Additionally, there are now helper functions for testing with `riak_ensemble` that provide reliable methods of waiting for the ensemble system to stabilize for testing. The uses of `timer:sleep` in this test should be replaced with usage of these helper functions.