add riak_test for admin_auth_enabled.
add riak_test for admin_auth_enabled.

basho/riak_cs,sdebnath/riak_cs,dragonfax/riak_cs,dragonfax/riak_cs,basho/riak_cs,laurenrother/riak_cs,basho/riak_cs,laurenrother/riak_cs,basho/riak_cs,sdebnath/riak_cs,GabrielNicolasAvellaneda/riak_cs,laurenrother/riak_cs,yangchengjian/riak_cs,yangchengjian/riak_cs,GabrielNicolasAvellaneda/riak_cs,GabrielNicolasAvellaneda/riak_cs,sdebnath/riak_cs,dragonfax/riak_cs,yangchengjian/riak_cs,dragonfax/riak_cs,sdebnath/riak_cs,GabrielNicolasAvellaneda/riak_cs,yangchengjian/riak_cs,laurenrother/riak_cs