OperationFailure should be raised for legacy "wnote" write concern error

RUBY-732
jnote should raise Mongo::Operation

RUBY-732
wnote should raise Mongo::OperationFailure

RUBY-732
Merge branch '1.x-stable-ruby-732' of https://github.com/gjmurakami-10gen/mongo-ruby-driver into gjmurakami-10gen-1.x-stable-ruby-732