nfsd: Continue adding macros so nfsd can run in a vnet prison

Commit 7344856e3a6d added a lot of macros that will front end
vnet macros so that nfsd(8) can run in vnet prison.
This patch adds some more of them and also a lot of uses of
nfsstatsv1_p instead of nfsstatsv1. nfsstatsv1_p points to
nfsstatsv1 for prison0, but will point to a malloc'd structure
for other prisons.

It also puts nfsstatsv1_p in nfscommon.ko instead of nfsd.ko.

MFC after: 3 months