Merge repl_rt_heartbeat test into 1.3

#### Overview 

Test was never merged to 1.3. Since HB exists on 1.3, and the fix for the heartbeat issue 390 needs to be merged, so the riak_test is required to test it.

It did require the rt_config module in the riak_test/src to be merge back as well. 

#### Issue

https://github.com/basho/riak_repl/issues/390