[Netapp/Nexenta] Move registration of config options

This doesn't really make a difference in practice, but
makes it possible for the sample config generator to figure
out the config group relationship when options are in one
file.

Change-Id: I3bc6ab5bcc85a8c11c9261b0d8c520fb846a7864
Merge "[Netapp/Nexenta] Move registration of config options"