knfsd: nfsd4: secinfo handling without secinfo= option

We could return some sort of error in the case where someone asks for secinfo
on an export without the secinfo= option set--that'd be no worse than what
we've been doing.  But it's not really correct.  So, hack up an approximate
secinfo response in that case--it may not be complete, but it'll tell the
client at least one acceptable security flavor.

Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>