[Security] User refreshment from identical users provider type

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

When we are using two privoders with the same supported class but with different users, there is a faill because the first `UsernameNotFoundException` will stop the refresh processus.
I assume that you want to achieve the situation where the framework doesn't throw an error when is able to find an user in any of user providers. 
I have a question: is it ok to log information about not found user even if he exists in at least one user provider? Maybe this should be logged just before end of the method, when you're quite sure that there is no existing user