Ignore result of list comprehensions.

Resolves:

riak_kv_entropy_manager.erl:218: Expression produces a value of type [any()], but this value is unmatched
riak_kv_entropy_manager.erl:262: Expression produces a value of type ['ok'], but this value is unmatched
riak_kv_entropy_manager.erl:395: Expression produces a value of type ['ok'], but this value is unmatched
riak_kv_entropy_manager.erl:502: Expression produces a value of type ['ok'], but this value is unmatched