Steps to reproduce:

1. In the web app as an admin user, go to Admin -> Manage Provisioning Requisitions
2. Enter "Foo" in the text box and click "Add New Requisition"
3. Edit the "Foo" requisition and add a node
4. Synchronize the "Foo" requisition and verify the node is created
5. Repeat steps 1 and 2, using the same name "Foo" as before

Expected result: web UI should indicate that the requested requisition name is already in use and kick the user back to the Manage Requisitions page

Actual result: web UI creates a new, empty requisition, overwriting the existing "Foo" requisition and deleting all the nodes it contains

Credit for spotting this to Jacob McNutt.