RUBY-1136 Don't delete entire os sub-document
RUBY-1136 Don't delete entire os sub-document

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