MB-10441: Adapt item_pager test for WIN32

It seems like the scheduling of the tasks is different on windows
(at least on my virtual machines). Once we have all of the tests
passing for WIN32 we're going to start benchmarking it so we'll
figure out a better fix for this at a later time..
For now just spend some time waiting for it to bump the values

Change-Id: I4446cd7ab3a42356dff9605d6a694c9aaed7fa00
Reviewed-on: http://review.couchbase.org/34428
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>