Add context parameter to authenticate call in riak_cs_wm_utils
Add context parameter to authenticate call in riak_cs_wm_utils

Fixes: CS365

The recent webmachine refactoring change the arity of authenticate
to 4. This updates the authenticate call in riak_cs_wm_utils to
reflect that.

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