Move end test logic out of individual workers.
Move end test logic out of individual workers.

Parent waits for the duration anyway, just make it unconditionally
kill the workers. They already had timeouts aborting them; they may
be in the middle of an operation, but we really don't care, time's up.

This also avoids oddities with the queue where there may be items
after the StopIteration.

This also avoids workers potentially not exiting within the 1-second
timeout the old code had.

ceph/s3-tests,dreamhost/s3-tests,timuralp/s3-tests,andrewgaul/s3-tests,Nexenta/s3-tests,dreamhost/s3-tests,Nexenta/s3-tests,smithfarm/s3-tests,robbat2/s3-tests,tobegit3hub/s3-tests,Intel-bigdata/s3-tests,smithfarm/s3-tests,andrewgaul/s3-tests,Nexenta/s3-tests,basho/s3-tests,ceph/s3-tests,SUSE/s3-tests,jmunhoz/s3-tests,tobegit3hub/s3-tests,basho/s3-tests,piousbox/s3-tests,jmunhoz/s3-tests,SUSE/s3-tests,piousbox/s3-tests,robbat2/s3-tests,Nexenta/s3-tests,Intel-bigdata/s3-tests,piousbox/s3-tests,timuralp/s3-tests