Increased the delay between sibling writes 

...so as to avoid races in resolution test.

Also added an option to skip the resolution test since it runs for ~5
seconds each invocation. This should fix the non-deterministic
failures in riak_test like
http://giddyup.basho.com/#/projects/riak/scorecards/35/35-387-client_python_verify-ubuntu-1004-64-eleveldb/14385/artifacts/76166

/cc @engelsanchez @javajolt

I verified the race is gone by running this:

```bash
$ for i in {1..20}; do python -m unittest riak.tests.test_all.RiakPbcTransportTestCase.test_resolution riak.tests.test_all.RiakHttpTransportTestCase.test_resolution; done
```