In the function "execute_action" is not taken into consideration return value that is returned by external script when lauching external script (if mediatype->type==MEDIA_TYPE_EXEC ).
This patch set the value for the variable res =SUCCEED if external script returned 0.
If external script return != 0 then res = FAIL.

In the Zabbix it is implemented in such way:

zabbix_server/alerter/alerter.c:
...
if(1 == execle(full_path,mediatype>exec_path,alert->sendto,alert->subject,alert->message,(char *)0, zbxenv))
...

But the problem is that "execle" return "-1" value in case when system error occured.
But need to return error code to the Zabbix from external script.