Listing keys still times out

The time-out detection code I just added checks for responses 'timeout' and also {error, {'timeout', _}}, but apparently we are very creative and can sometimes return {error, <<"timeout">>}, like here:

http://giddyup.basho.com/#/projects/riak/scorecards/9/9-291-loaded_upgrade-ubuntu-1004-32-eleveldb-previous/3340

We need to check for that too and prevent the test from failing from a simple time out