vl.c: reduce exit on error code duplication

use error_report_fatal() helper instead of a bunch of
    if (local_err) {
        error_report(foo);
        error_free(local_err);
        exit(1);
    }
code blocks

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 * s/exit_if_error/error_report_fatal/
 * move error_report_fatal() into util/error.c