Avoid infinite loop when the telnet session is closed client-side.

Signed-off-by: Rémi Denis-Courmont <rdenis@simphalempin.com>

modules/control/telnet.c

@@ -379,7 +379,7 @@ static void Run( intf_thread_t *p_intf )
                     errno = EAGAIN;
                 }
 #endif
-                if (i_recv <= 0 && ( end || errno != EAGAIN ) )
+                if( i_recv == 0 || ( i_recv == -1 && ( end || errno != EAGAIN ) ) )
                     goto drop;
             }
         }