R1:ca17e2283d92

Have Maniphest use create transactions when using email

Summary: Fixes T12929. Sets a create transaction if new.

Test Plan: test a new task over email via command line

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12929

Differential Revision: https://secure.phabricator.com/D18279