verify_counter_converge should retry on not found [JIRA: RIAK-1911]

[macintux]

Seeing occasional test failures where the request gets a not found and counts it as a failure, instead of retrying.

{{badmatch,{error,{ok,"404",
                      [{"Server","MochiWeb/1.1 WebMachine/1.10.6 (no drinks)"},
                       {"Date","Sat, 27 Jun 2015 19:46:54 GMT"},
                       {"Content-Type","text/plain"},
                       {"Content-Length","10"}],
                      <<"not found\n">>}}},
 [{verify_counter_converge,get_counter,2,
                           [{file,"tests/verify_counter_converge.erl"},
                            {line,95}]},
  {verify_counter_converge,'-confirm/0-fun-4-',2,
                           [{file,"tests/verify_counter_converge.erl"},
                            {line,60}]},
  {verify_counter_converge,'-confirm/0-lc$^4/1-4-',1,
                           [{file,"tests/verify_counter_converge.erl"},
                            {line,60}]},
  {verify_counter_converge,confirm,0,
                           [{file,"tests/verify_counter_converge.erl"},
                            {line,60}]},
  {riak_test_runner,return_to_exit,3,
                    [{file,"src/riak_test_runner.erl"},{line,159}]}]}

[russelldb]

Addressed by 81e7107 in nhs-riak/riak_test/rdb/nhs-riak-2.2.5. Will ref this issues when I open PRs as part of 2.2.5 release