nfsd4: name->id mapping should fail with BADOWNER not BADNAME

According to rfc 3530 BADNAME is for strings that represent paths;
BADOWNER is for user/group names that don't map.

And the too-long name should probably be BADOWNER as well; it's
effectively the same as if we couldn't map it.

Cc: stable@kernel.org
Reported-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Reported-by: Simon Kirby <sim@hostway.ca>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --cc fs/nfsd/nfs4idmap.c
Simple merge

diff --cc fs/nfsd/nfsd.h
Simple merge

diff --cc fs/nfsd/nfsproc.c
Simple merge