[bugfix] fix the isinstance call in ThreadList initializer
[bugfix] fix the isinstance call in ThreadList initializer

- fix isinstance call which must be (object, classinfo)
- use a wait_time parameter instead of a constant two seconds time
- add documentation

Change-Id: I53aa147f3e0e2d7fcc5451ffc0f9de4b9012faaa

PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core