[ticket/12844] Don't clear $dbpasswd early in connection manager

PHPBB3-12844
Merge pull request #2727 from Nicofuma/ticket/12844

[ticket/12844] Don't clear $dbpasswd early in connection manager

* Nicofuma/ticket/12844:
  [ticket/12844] Don't clear $dbpasswd early in connection manager
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12844] Don't clear $dbpasswd early in connection manager