add Vyatta to unix group for observium_agent support

Vyatta is just running a custom debian os, so Vyatta should be added to to the unix group?

That way the observium_agent runs also fine on a Vyatta router...

Index: includes/definitions/os.inc.php
===================================================================
— includes/definitions/os.inc.php (revision 4847)
+++ includes/definitions/os.inc.php (working copy)
@@ -36,6 +36,7 @@
$config['os'][$os]['text'] = "Vyatta";
$config['os'][$os]['type'] = "network";
$config['os'][$os]['ifname'] = 1;
+$config['os'][$os]['group'] = "unix";
$config['os'][$os]['snmp']['max-rep'] = 100;
$config['os'][$os]['over'][0]['graph'] = "device_bits";
$config['os'][$os]['over'][0]['text'] = "Traffic";