If a branch that is to be deleted happens to be a symref to another
branch, the current code removes the targeted branch instead of the
one it was called for.
Change this surprising behaviour and delete the symref branch
instead.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx> Signed-off-by: Junio C Hamano <gitster@pobox.com>