Resolve a series of match warnings.

Resolves:

riak_kv_console.erl:320: Expression produces a value of type ['ok'], but this value is unmatched
riak_kv_console.erl:336: Expression produces a value of type ['ok'], but this value is unmatched
riak_kv_console.erl:349: Expression produces a value of type ['ok'], but this value is unmatched
riak_kv_console.erl:643: Expression produces a value of type 'ok' | ['ok'], but this value is unmatched