Fix for loop count issue when do_verify=0 (#1093)

Fix for loop count issue when do_verify=0 (#1093)

'clear_io_state' is called twice and resets the nr_done_files.
'clear_io_state' resets the nr_done_files if loop>=1.
This API is called twice with in thread_main and the second call is
skipped if do_verify=0. We rely on the first call for setup management.
So, for the very last loop, we would have skipped reseting
'nr_done_files' because loops=0 resulting in an IO error
in do_io and we exit without performing any IOs. Fix will invoke
the second call to clear_io_state

Signed-off-by: Sowmya Ravi sowmyaravi.92@gmail.com