fix trace disconnect

when analyzing trace informatien we disconnect the context in upload.go:
```go

func (store OcisStore) CreateNodeForUpload(session *OcisSession, initAttrs node.Attributes) (*node.Node, error) {
ctx, span := tracer.Start(session.Context(context.Background()), "CreateNodeForUpload")
```

this leads to the trace information for an upload not showing what is going on in CreateNodeForUpload:

What happens in these 280ms?

traces produced with https://github.com/cs3org/reva/pull/4978

Start in upload.go at OcisStore.CreateNodeForUpload and inspect how session.Context(context.Background()) is passed to tracer.Start. Compare the upload trace with the traces from reva PR #4978 to find where the parent context is lost. Done means the work inside CreateNodeForUpload appears in the upload trace without the unexplained 280ms disconnect.

Written by the indexing model from the issue text.