Fix up redirectors can fail if some packages were already checked out

1. Create a project that is managed by source control (bug was discovered using Perforce as source control)
2. Import/add a static mesh, then create a new material and assign it to the Static Mesh
3. Push both the assets to your source control
4. Move the material to a new folder, accepting the prompt to check out the asset (this should leave a redirector asset in its place)
5. Check out the static mesh asset from source control
6. Create a c++ function (blueprint callable) matching the below code. Specifically calling AssetTools.FixupReferences() and setting bCheckoutDialogPrompt to FALSE
7. Call the function you created from an editor blueprint, passing in the path to the redirector asset for the material
8. Expected result: the redirector was full fixed up and subsequently deleted because it’s only reference is already checked out (and therefore modifiable)

Actual Result: the redirector will not be fully fixed up and a warning message will appear saying that the static mesh asset was not checked out due to the static mesh asset not being checked out from source control

(As a follow up, if you do the process again, but set bCheckoutDialogPrompt to TRUE the function will perform as expected and fully fix up the redirector)