RUBY-1174 Add #unknown? method on cluster double
RUBY-1174 Add #unknown? method on cluster double

jonhyman/mongo-ruby-driver,kay-kim/mongo-ruby-driver,jonhyman/mongo-ruby-driver,mongodb/mongo-ruby-driver,mongodb/mongo-ruby-driver,kay-kim/mongo-ruby-driver,saghm/mongo-ruby-driver,estolfo/mongo-ruby-driver,mongodb/mongo-ruby-driver,saghm/mongo-ruby-driver,estolfo/mongo-ruby-driver