ipvs: Remove unused variable ret from sync_thread_master()

net/netfilter/ipvs/ip_vs_sync.c: In function 'sync_thread_master':
net/netfilter/ipvs/ip_vs_sync.c:1640:8: warning: unused variable 'ret' [-Wunused-variable]

Commit 35a2af94 ("sched/wait: Make the
__wait_event*() interface more friendly") changed how the interruption
state is returned. However, sync_thread_master() ignores this state,
now causing a compile warning.

According to Julian Anastasov <ja@ssi.bg>, this behavior is OK:

    "Yes, your patch looks ok to me. In the past we used ssleep() but IPVS
     users were confused why IPVS threads increase the load average. So, we
     switched to _interruptible calls and later the socket polling was
     added."

Document this, as requested by Peter Zijlstra, to avoid precious developers
disappearing in this pitfall in the future.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

net/netfilter/ipvs/ip_vs_sync.c

@@ -1637,7 +1637,10 @@ static int sync_thread_master(void *data)
 			continue;
 		}
 		while (ip_vs_send_sync_msg(tinfo->sock, sb->mesg) < 0) {
-			int ret = __wait_event_interruptible(*sk_sleep(sk),
+			/* (Ab)use interruptible sleep to avoid increasing
+			 * the load avg.
+			 */
+			__wait_event_interruptible(*sk_sleep(sk),
 						   sock_writeable(sk) ||
 						   kthread_should_stop());
 			if (unlikely(kthread_should_stop()))