Add missing specs for `#find_or_initialize_with_errors`
Add missing specs for `#find_or_initialize_with_errors`

After merging https://github.com/plataformatec/devise/pull/4797, I
noticed that we had no specs for the scenarios where this method was
adding the errors to the resource. This commit adds tests to cover those
cases.

plataformatec/devise,rubyrider/devise,Qwiklabs/devise,rubyrider/devise,Qwiklabs/devise,plataformatec/devise,rubyrider/devise