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

commit f6af99ec1b261e21219d5eba99e3af48fc6c32d4 upstream.

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.

Reported-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Reported-by: Simon Kirby <sim@hostway.ca>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>