CS-15406 [2.2.14 to 3.0.4 upgrade] Hosts going to Alert state after upgrade as it cann't find any name-label set to "cloud-private"

Reviewed-By: Alena

Changes:
- Looks like we cannot default to 'cloud-private' label.
- If it is not set, CS figures out the default management interface and usus its name.
- We will use the global config variable as the label. if it is null, the label on the physical network will be null.

server/src/com/cloud/upgrade/dao/Upgrade303to304.java

@@ -104,10 +104,6 @@ public class Upgrade303to304 extends Upgrade30xBase implements DbUpgrade {
                         //Decrypt this value.
                         xenGuestLabel = DBEncryptionUtil.decrypt(xenGuestLabel);
                         
-                        if(xenGuestLabel == null){
-                            xenGuestLabel = "cloud-private";
-                        }
-                        
                         //Create a physical network with guest traffic type and this tag
                         long physicalNetworkId = addPhysicalNetworkToZone(conn, zoneId, zoneName, networkType, null, domainId);
                         addTrafficType(conn, physicalNetworkId, "Guest", xenGuestLabel, null, null);