[Security] Fixed problem with losing ROLE_PREVIOUS_ADMIN role.

<table>
  <tr>
    <td><b>Q</b></td>
    <td><b>A</b></td>
  </tr>
  <tr>
    <td>Bug fix?</td>
    <td>yes</td>
  </tr>
  <tr>
    <td>New feature</td>
    <td>no</td>
  </tr>
  <tr>
    <td>BC breaks?</td>
    <td>no</td>
  </tr>
  <tr>
    <td>Deprecations?</td>
    <td>no</td>
  </tr>
  <tr>
    <td>Tests pass?</td>
    <td>yes</td>
  </tr>
  <tr>
    <td>Fixed tickets</td>
    <td>#3085, #8974</td>
  </tr>
  <tr>
    <td>License</td>
    <td>MIT</td>
  </tr>
  <tr>
    <td>Doc PR</td>
    <td>n/a</td>
  </tr>
</table>

Problem occurs while user is impersonated. Authentication process generates new token and doeas not preserve role ```ROLE_PREVIOUS_ADMIN```. Ex. when parameter ```security.always_authenticate_before_granting``` is enabled.