dbench cleanup bug

[Steve French]

Some of our testers noticed that dbench (even Tridge's most current 
version) does not wait long enough before doing the cleanup phase - ie 
before doing the equivalent of "rm -rf" (nb_cleanup which calls 
nb_deltree) immediately after the end the test - which can cause sharing 
violations when run against Windows servers (as "rm -rf" is racing 
against the close of the test cases file handles).

Any thoughts about whether dbench should be changed to sleep a few 
seconds before the cleanup phase starts (or add an option to sleep a few 
seconds- there already is an option to skip cleanup)?