Fix security issue in _prolog_error().

Fix security issue caused by insecure file path handling triggered by
the failure of a Prolog script. To exploit this a user needs to
anticipate or cause the Prolog to fail for their job.

(This commit is slightly different from the fix to the 15.08 branch.)

CVE-2016-10030.
_rpc_reconfig(slurm_msg_t *msg)
{
	uid_t req_uid = g_slurm_auth_get_uid(msg->auth_cred,
					     conf->auth_info);

	if (!_slurm_authorized_user(req_uid))
		error("Security violation, reconfig RPC from uid %d",
		      req_uid);
	else
		kill(conf->pid, SIGHUP);
	forward_wait(msg);
	/* Never return a message, slurmctld does not expect one */
}

_rpc_reconfig(slurm_msg_t *msg)
{
	uid_t req_uid = g_slurm_auth_get_uid(msg->auth_cred,
					     conf->auth_info);

	if (!_slurm_authorized_user(req_uid))
		error("Security violation, reconfig RPC from uid %d",
		      req_uid);
	else
		kill(conf->pid, SIGHUP);
	forward_wait(msg);
	/* Never return a message, slurmctld does not expect one */
}
