nfssrv: need ability to go to submounts for v3 and v2 protocols
RFCs of NFSv3,v2 protocols don't have mentions for submounts, but for NFSv4 does.
illumos nfs server doesn't go to submounts automatically. Therefore nfs v2,v3-clients need
to be configured with automounter to use exported submounts.
It can be problematic for some nfs-clients. For instance, ESX-server (it uses nfs v3).
Solution: add option for exported NFS-share: "nohide". If share has this option, this exported sub-share will be seen by NFS v2,v3 clients.
By default "nohide" is off.