[Bug] Register From is refilled with Encrypted Phone Number when email is duplicated

Summary

The phone field is refilled with an unexpected string on register page if the email is duplicated in database.

Steps to reproduce

1. open the register page
2. fill the register from with correct values
3. change the email input with an existing email address, it means that the email address should be an email from a registered SaaS user.
4. submit the form
5. then you should see the email validation fails and the phone input is refilled with an encrypted string.

Example Project

What is the current bug behavior?

Phone Input value is refilled with an encrypted string.

What is the expected correct behavior?

Phone input value should be the previous phone number typed by user or kept blank.

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes