fix(authenticator): Restart flow for second password attempt

[mattcreaser]

• PR conforms to Pull Request guidelines.

Issue #, if available:

Description of changes:
If a user only has password as an available authentication factor during a UserChoice sign and then enters an invalid password, they would get stuck into an invalid state and not be able to try to correct the password (ultimately due to this Amplify bug). This change works around the issue by restarting the sign in flow if a user is retrying to enter a password.

This is the same logic that was already in place for the multi-factor case here.

How did you test these changes?
(Please add a line here how the changes were tested)

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Ensure commit message has the appropriate scope (e.g fix(liveness): message, fix(authenticator): message, fix(all): message)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.