Fix Newsletter Subscribe Workflow

[torhoehn]

Description

This pull request fixes that the newsletter confirmation email will be sent multiple times and that the Confirmation Succes and Unsubscription Email will be sent at the correct states.

Fixed Issues (if relevant)

1. Multiple newsletter confirmation emails sent #12876: Multiple newsletter confirmation emails sent

Manual testing scenarios

1. Change configuration under Stores > Configuration > Customers > Newsletter > Subscription Options > Need to Confirm to Yes

2. Sign up for Newsletter on frontend as a guest

3. Follow confirmation link in email

4. Create an account and check Sign Up for Newsletter within the form and use the same email as in Step 2

5. Go to your customer account edit

6. Save your customer account without changing anything

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[dmanners]

Hi @torhoehn thank you for this pull request. Currently the static tests are failing in travis. Could you take a look at the following issue for me.

There was 1 failure:
1) Magento\Test\Php\LiveCodeTest::testCodeStyle
PHP Code Sniffer detected 2 violation(s): 
FILE: ...is/build/magento/magento2/app/code/Magento/Newsletter/Model/Subscriber.php
--------------------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
--------------------------------------------------------------------------------
 617 | ERROR | [x] Inline control structures are not allowed
--------------------------------------------------------------------------------
PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
--------------------------------------------------------------------------------

Thank you

[dmanners]

@torhoehn thank you for the quick update. I will process this PR now for you.