hugolib: Fix layout lookup order for Render func

hugolib: Fix layout lookup order for Render func

Will have to fix this in a better way later in relation to the non-renderable pages.

But this commit brings the Hugo Benchmark down to "only slightly slower" than master.

```
benchmark           old ns/op       new ns/op       delta
BenchmarkHugo-4     10074504521     10071236251     -0.03%

benchmark           old allocs     new allocs     delta
BenchmarkHugo-4     43623091       49271859       +12.95%

benchmark           old bytes      new bytes      delta
BenchmarkHugo-4     9468322704     9725848376     +2.72%
```

Which is something we can work with.