Preserve "Space" UI control value when editing Passphrase credentials

Summary: Fixes T9568. We just weren't setting this properly so it would default away from the proper value.

Test Plan:

• Edited a credential in a non-default space, edit form populated properly.
• Changed "Space", introduced an error, saved form, got error with sticky value for "Space" properly.
• Saved form with new space value.
• Created a new credential.

Reviewers: chad

Reviewed By: chad

Subscribers: revi

Maniphest Tasks: T9568

Differential Revision: https://secure.phabricator.com/D14278