bug fixes from Fujitsu (bug 24)

```-------------------------------------------------------
bug 24

Ttile:
The last line "multicast_group = multicast_group" is hard
to understand. The local variable should be different name
than the global variable.

Bug Location:
const char *multicast_group_list[MULTICAST_LINK_NUM_GROUPS] = {
  "239.0.0.161",
  "239.0.0.162",
  "239.0.0.163",
  "239.0.0.164"
};
:
:
void multicast_link_start(void (*rx_handlerP) (unsigned int, char *),
                          unsigned char multicast_group, char *multicast_ifname)
{
  rx_handler = rx_handlerP;
  multicast_group = multicast_group;

Note:
Detected by CppCheck
```

-------------------------------------------------------

openair1/SIMULATION/ETH_TRANSPORT/multicast_link.c

@@ -308,10 +308,10 @@ void* multicast_link_main_loop (void *param)
 }
 
 void multicast_link_start(void (*rx_handlerP) (unsigned int, char *),
-                          unsigned char multicast_group, char *multicast_ifname)
+                          unsigned char _multicast_group, char *multicast_ifname)
 {
   rx_handler = rx_handlerP;
-  multicast_group = multicast_group;
+  multicast_group = _multicast_group;
   multicast_if =  multicast_ifname;
   LOG_I(EMU, "[MULTICAST] LINK START on interface=%s for group=%d: handler=%p\n",
         (multicast_if == NULL) ? "not specified" : multicast_if, multicast_group,