Fix stream buckets with timeout
Fix stream buckets with timeout

The wrong guard was used for bucket types, causing a call with a timeout
to fail. This fixes a problem found running the verify_api_timeouts riak
test

SiftLogic/riak-erlang-client,paulperegud/riak-erlang-client,linearregression/riak-erlang-client,jmayfield74/riak-erlang-client,pma/riak-erlang-client,GabrielNicolasAvellaneda/riak-erlang-client,inaka/riak-erlang-client,rhumbertgz/riak-erlang-client,esl/riak-erlang-client,groovenauts-erlang/riak-erlang-client