user management: show password error temporary

[michag86]

Fixes #21239

[mention-bot]

By analyzing the blame information on this pull request, we identified @ringmaster, @MorrisJobke and @PVince81 to be potential reviewers

[MorrisJobke]

👍

[MorrisJobke]

@owncloud/javascript Please review :)

[blizzz]

while testing I found

{"reqId":"1SQkp1HkxbWCja380dE+","remoteAddr":"127.0.0.1","app":"PHP","message":"Undefined variable: l at \/home\/blizzz\/owncloud\/dev\/master\/settings\/changepassword\/controller.php#154","level":0,"time":"2015-12-17T13:52:51+00:00","method":"POST","url":"\/master\/index.php\/settings\/users\/changepassword"}
{"reqId":"1SQkp1HkxbWCja380dE+","remoteAddr":"127.0.0.1","app":"PHP","message":"Call to a member function t() on null at \/home\/blizzz\/owncloud\/dev\/master\/settings\/changepassword\/controller.php#154","level":3,"time":"2015-12-17T13:52:51+00:00","method":"POST","url":"\/master\/index.php\/settings\/users\/changepassword"}

which is unrelated by this PR. Easy fix, will provide in a seperate PR, and with this it works as expected 👍