remove obsolete pywikibot.stopme() at the end of some other scripts.

In core branch pywikibot.stopme() is called by atexit library.
The function is executed upon normal program termination. This
patch prohibits executing it twice.

Change-Id: Id6881a166b0e7032a78c09654dd1e6d5a5649590
Merge "remove obsolete pywikibot.stopme() at the end of some other scripts."