In ApplicationTransactionEditor, determine new objects with "getID()" instead of "getPHID()"
Summary:
See <https://discourse.phabricator-community.org/t/unable-to-reload-object-that-hasnt-been-loaded/2677>.
When editing "Config" objects, they currently get a PHID set outside of the TransactionEditor. They probably should not, but fixing that is likely an involved change.
This causes us to incorrectly fail to detect `$is_new` correctly and try to `reload()` and object with no ID.
To work around this, test for new objects with `getID()` instead of `getPHID()`.
Test Plan: Edited any config value with the web UI.
Reviewers: amckinley
Differential Revision: https://secure.phabricator.com/D20482