[Conf] Rename and fix RBL_VIRUSFREE symbol

conf/modules.d/rbl.conf

@@ -122,7 +122,7 @@ rbl {
             rbl = "bip.virusfree.cz";
             ipv6 = true;
             returncodes {
-                RBL_VIRUSFREE_BLACK = "127.0.0.1";
+                RBL_VIRUSFREE_BOTNET = "127.0.0.2";
             }
         }
     }

conf/scores.d/rbl_group.conf

@@ -150,8 +150,8 @@ symbols = {
         description = "Address is listed in Spameatingmonkey RBL (ipv6)";
     }
 
-    "RBL_VIRUSFREE_BLACK" {
+    "RBL_VIRUSFREE_BOTNET" {
         weight = 2.0;
-        description = "From address is listed in virusfree.cz BL";
+        description = "Source IP is listed in virusfree.cz BL";
     }
 }