maintenance/importImages: Don't sleep after the last upload

maintenance/importImages: Don't sleep after the last upload

Currently, the importImages maintenance script offers an option
to sleep an arbitrary amount of seconds after each upload.

The current logic implementation had a side effect to also sleep
after the last image upload. This is not a desired behavior, as
the tasks are done and a clean exit with a report are welcome.

Instead, sleep will now occur before the second upload and the
ones to follow.

Change-Id: Ia675f210582c3075e9b59b002a00cb1fc4b44cac