Controller ensureInLayer is slow when using addReads/addOpens for Layers with large numbers of modules

[Thomas Watson]

> I agree, we can trivially fix this, it just wasn't noticed before.
> 
> -Alan

The fix for this is in the latest jigsaw builds.  I tested it out and see 
10x improvement when using the controller for layers with over 100 
modules.  I also see nearly 2x improvement for layers with only 1 module.

Thanks Alan!

Tom