init: fix segfaul in iscsi_parse_url

We allowed iscsi to be NULL in iscsi_parse_url. Especially
qemu does this and currently segfaults at start. Change the
usage guidelines for target username/password to be the same
as for chap username/password.

Signed-off-by: Peter Lieven <pl@kamp.de>

include/iscsi.h

@@ -91,6 +91,8 @@ struct iscsi_url {
        char target[MAX_STRING_SIZE + 1];
        char user[MAX_STRING_SIZE + 1];
        char passwd[MAX_STRING_SIZE + 1];
+       char target_user[MAX_STRING_SIZE + 1];
+       char target_passwd[MAX_STRING_SIZE + 1];
        int lun;
        struct iscsi_context *iscsi;
 };