If a findAndModify command with upsert=true inserted a new document and new=false, it will return null as the value. Currently, a retry of this command does not return null, like it should.

Failing retryable_writes_jscore_passthrough tests:

• find_and_modify4.js
• find_and_modify_empty_coll.js
• find_and_modify_empty_update.js
• find_and_modify_server6226.js