DRA e2e: fix error reporting in test driver

Dropping the error that is returned by allocateOne hides the reason *why*
allocation failed. Including the UID is "too much information" for an error
message (usually the user doesn't care about the exact identity, just the name)
and the claim name can and will be added by the caller.

test/e2e/dra/test-driver/app/controller.go

@@ -241,7 +241,7 @@ func (c *ExampleController) allocateOneByOne(ctx context.Context, claimAllocatio
 	for _, ca := range claimAllocations {
 		allocationResult, err := c.allocateOne(ctx, ca.Claim, ca.ClaimParameters, ca.Class, ca.ClassParameters, selectedNode)
 		if err != nil {
-			ca.Error = fmt.Errorf("failed allocating claim %v", ca.Claim.UID)
+			ca.Error = err
 			continue
 		}
 		ca.Allocation = allocationResult