Currently, whenever svn repository http server requests client
certificate, prompt provider is invoked, ignoring any
ssl-client-cert-file settings in ~/.subversion/servers.
Moreover, it happens more than once per session, which is quite
irritating.
Signed-off-by: Michael Krelin <hacker@klever.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>