Steps to reproduce

1. use the user_ldap plugin (which updates the avatar from LDAP after each login: https://github.com/owncloud/user_ldap/blob/master/lib/User/User.php#L474-L483)
2. set a user image in LDAP
3. watch as the PHOTO field is repeatedly added to the user's vCard blob in oc_cards, until the database can hold no more (triggering Truncate Doctrine\DBAL\Exception\DriverException message if too long doctrine/dbal#2523 in passing)

Expected behaviour

Only one PHOTO field is present in the vCard

Actual behaviour

Duplicate PHOTO fields keep getting added to the user's vCard

Cause

Converter::updateCard unconditionally adds the given photo to the vCard, rather than replace it:

Server configuration

Operating system: OpenBSD 6.0

Web server: apache-httpd-2.4.23

Database: MySQL (mariadb-server-10.0.25p0v1)

PHP version: php-5.6.23p0

ownCloud version: (see ownCloud admin page) 9.0.2

Updated from an older ownCloud or fresh install: updated

Where did you install ownCloud from: OpenBSD ports