Avoid to mark a site initialized on failure

Summary:
Check the recipe status to be successful, and if not, don't mark
as initialized.

Init script should be documented to use the following exit codes:

• Success: 0
• Failure: 2

Test Plan: alkane init

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D3015