service: add options RestartPreventExitStatus and SuccessExitStatus

In some cases, like wrong configuration, restarting after error
does not help, so administrator can specify statuses by RestartPreventExitStatus
which will not cause restart of a service.

Sometimes you have non-standart exit status, so this can be specified
by SuccessfulExitStatus.

src/core/socket.c

@@ -1884,7 +1884,7 @@ static void socket_sigchld_event(Unit *u, pid_t pid, int code, int status) {
 
         s->control_pid = 0;
 
-        if (is_clean_exit(code, status))
+        if (is_clean_exit(code, status, NULL))
                 f = SOCKET_SUCCESS;
         else if (code == CLD_EXITED)
                 f = SOCKET_FAILURE_EXIT_CODE;