Bug: UploadObject with `if-none-match` returns 500 instead of 412

[itaiad200]

If the object exists, the returned response to the client is 500 instead of 412. At this line we check for graveler.ErrPreconditionFailed, but the code returns kv.ErrPreconditionFailed.

An error log from v0.102.2 that returns 500:

log | {"error":"predicate failed","file":"build/pkg/api/controller.go:2069","func":"pkg/api.(*Controller).handleAPIErrorCallback","host":"***","level":"error","method":"POST","msg":"API call returned status internal server error","operation_id":"UploadObject","path":"/api/v1/repositories/<REPO>/branches/<BRANCH>/objects?path=<PATH>","request_id":"<>","service":"api_gateway","service_name":"rest_api","time":"2023-06-20T20:12:59Z","user":"<USER>"}