generic/192: use shorter sleep and tolerate 2s delay

generic/192: use shorter sleep and tolerate 2s delay

generic/192 would sleep 40 seconds, update a file's atime, and then
fail if the atime was not exactly 40 seconds later.  This is
unreliable since things may be slow enough to cause an extra second
to elapse.  "Fix" this by allowing for 2 seconds of delay.  Also,
while we're at it shorten the sleep to a much more reasonable 5
seconds.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>