NFS: move dprintk after nfs_alloc_fattr in nfs3_proc_lookup

In nfs3_proc_lookup, if nfs_alloc_fattr fails, will only print
"NFS call lookup". This may be confusing, move dprintk after
nfs_alloc_fattr.

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>