DEV-2387 introduced a log_size varibale which is never decreased, so after some time of working zabbix is starting throwing errors

https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/src/libs/zbxembed/zabbix.c#81{}

Steps to reproduce:

1. Use function Zabbix.Log(); in any JavaScript preprocessing, like in template "Asterisk by HTTP"

Result:

Errors in logs:
<time> error reason for "<host>:asterisk.get_stats" changed: Preprocessing failed for: HTTP/1.1 200 OK..Server: <server>..Date: <date>..Cache-Control: n...
1. Failed: Error: log exceeds the maximum size of 8388608 bytes.
at [anon] (zabbix.c:84) internal
at [anon] () native strict preventsyield
at [anon] (function:10)
at [anon] (function:256) preventsyield