NFS: Simplify nfs_fhget()

If the inode is being initialised, there is no point in
setting flags such as NFS_INO_INVALID_ACCESS,
NFS_INO_INVALID_ACL or NFS_INO_INVALID_DATA since there are
no cached access calls, acls or data caches to invalidate.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>