Fix Error 500 when relative submodule resolves to a namespace that has a different name from its path
### What does this MR do?
This MR fixes a bug in resolving a namespace when the `name` differed from `path`.
### Why was this MR needed?
The original code was using `name`, when the proper input to `namespace_project_path` was `path`.
### What are the relevant issue numbers?
Closes#1849
See merge request !864