Normalize riak_test execution process

Currently the execution of the riak_test modules for yokozuna relies on some specific setup assumption contained in the `tools/verify.sh` script. The focus of this issue is to bring the execution of the yokozuna tests inline with way other riak_tests are executed. This seems appropriate now that yokozuna is a part of riak proper. This will make it easier for people to get the tests up and running and facilitate the testing of yokozuna features in concert with other riak features.

My initial thoughts of the things needed are as follows: 

* [x] Remove requirement of extra step to build the yokozuna basho_bench driver prior to executing riak_test modules.
* [x] Change the expectation for where the `yz_security` test looks for the cert file. 
* [x] Update basho_bench setup and expectations to break the reliance on `verify.sh` and `misc/bench` in the yokozuna repo
* [x] Update the TESTING.md document to reflect the new procedures to run riak_test with yokozuna

There may be other items or hurdles that crop up, but this issue is to represent the exploratory work to attempt this.

cc: @engelsanchez