microLB no longer builds with NaCl

[AndreasAakesson]

The microLB constructor has changed multiple times on dev (related change: 612c86d), which makes NaCl outdated. From what I can see it's no longer possible to just change the one line constructing the object, since the option of either tcp, s2n or openssl. I'm not sure if this means the load balancer NaCl object also needs to extended or changed (@fwsGonzo and @AnnikaH maybe can see this).

It's also obvious either the OS test suite or NaCl needs to take responsible for making sure the microLB is actually built by NaCl to avoid changes like this going undiscovered.

[fwsGonzo]

Did we solve this? By just making a constructor parameter have a default value, or something.