I just upgraded a week or so ago to 2.1.5 and noticed I needed to re-enter my password for wifi. Which I've been too lazy to look up.
So, I'll try to do that, connect, and then see whether it asks me again a second time when connecting a second time.
I'd done the upgrade to 2.0.1 just fine without needing to re-enter my password. Since the password was set by my neighbor (we share wifi), it's so hard for me to remember. hence, my laziness on re-entering it to my kobo.