Allow additional network adapters - new soft limit: 16

[MarkProminic]

I have a use case/want to use more than 8 network adapters in bhyve.

I am proposing this fix as suggested by Peter Tribble (thanks!) as discussed here:

https://illumos.topicbox.com/groups/omnios-discuss/Tfff6c6e0a407dbba

[citrus-it]

I have no idea what github has managed to do now. I've opened #489 with this change plus the whitespace fix that @hadfl requested.