Don't busywait on a variable with 1 sec resolution

We can always live with almost a sec delay (since the tests
is doing too many sleeps anyway). The code is capable of running
a lot of stats per sec.

Change-Id: Ie94a99cd6390cb7e1849801b5b489188b2399589
Reviewed-on: http://review.couchbase.org/33804
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>