sgw: egress file: use full time resolution on Linux
sgw: egress file: use full time resolution on Linux

When checking the file modification time. The file might change
again in the same second that it was last read.

Signed-off-by: Ferry Huberts <66e11f9f5d965b69497c7e73d5e808f8b13c1218@pelagic.nl>

diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap,diogomg/olsrd-binary-heap