nfsd: fix dentry refcounting on create

b44061d0

 introduced a dentry ref counting bug.  Previously we were
grabbing one ref to dchild in nfsd_create(), but with the creation of
nfsd_create_locked() we have a ref for dchild from the lookup in
nfsd_create(), and then another ref in nfsd_create_locked().  The ref
from the lookup in nfsd_create() is never dropped and results in
dentries still in use at unmount.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Fixes: b44061d0

 "nfsd: reorganize nfsd_create"
Reported-by: kernel test robot <xiaolong.ye@intel.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>