test_sleep: More latency workarounds

We are also seeing qemu failures in the synchronous wakeup tests,
where the fiber should be resuming instantly but in practice sees a
one-tick delay due to the emulation environment not being
deterministic.  Allow one tick of slop in those too.

Change-Id: Idab7c45ea0b10bd955b90a98d3884b5fe0571187
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>