fix: fdb tables multiple IPs and IPs from other devices adding extra rows (#6930)

Fix missing IPs because the ARP entries are on different port_id
Update arp discovery to use snmpwalk_group() additional fix in that function
Fix removal of arp entries
Fix a debug output type in fdb discovery

includes/snmp.inc.php

@@ -561,7 +561,7 @@ function snmpwalk_group($device, $oid, $mib = '', $depth = 1, $array = array())
         // merge the parts into an array, creating keys if they don't exist
         $tmp = &$array;
         foreach ($parts as $part) {
-            $tmp = &$tmp[$part];
+            $tmp = &$tmp[trim($part, '"')];
         }
         $tmp = trim($value, "\" \n\r"); // assign the value as the leaf
     }