Enable to skip sending reconfirmation email when reconfirmable is on and skip_confirmation_notification! is invoked

We could always generate a confirmation token but not sending a
confirmation email by invoking the skip_confirmation_notification!
method when creating the account.
But there were no way to do that when we were turning on reconfirmable
and updating email.
By merging this PR, it will be possible :)

Thank you.

ref: #2468 

PS:
The build is failing due to a problem in travis ci, does anyone know how to retry build :( ?