fs/rc/jobs: ExecuteJob propagate the error returned by function

Without this patch the resulting error is first converted to string and then recreated.
This makes it impossible to use the defined error types to figure out the cause of the error,
and may result in invalid HTTP status codes.

This patch adds a test TestExecuteJobErrorPropagation to validate that the errors are
properly propagated.

fs/rc/jobs/job_test.go

@@ -213,6 +213,17 @@ func TestExecuteJob(t *testing.T) {
 	assert.Equal(t, int64(1), id)
 }
 
+func TestExecuteJobErrorPropagation(t *testing.T) {
+	jobID = 0
+
+	testErr := errors.New("test error")
+	errorFn := func(ctx context.Context, in rc.Params) (out rc.Params, err error) {
+		return nil, testErr
+	}
+	_, _, err := ExecuteJob(context.Background(), errorFn, rc.Params{})
+	assert.Equal(t, testErr, err)
+}
+
 func TestRcJobStatus(t *testing.T) {
 	jobID = 0
 	_, err := StartAsyncJob(longFn, rc.Params{})