As the source of last resort try checking if owner and owner_group in
NFSv4 attributes is purely numeric value. If the check passes then
assume that ID is good and add it to the in-core cache - this deals with
servers which return IDs in form 17@myhost.

Ported from 1.5.x:  9563819d197378b1563523fcb237e61e6e8543f8
Original author: Max Matveev <makc@gmx.co.uk>

Signed-off-by: suhrud <supatank@in.ibm.com>