SUNRPC: Add cond_resched() at the appropriate point in __rpc_execute()

Allow tasks that need to pre-empt rpciod/xprtiod to do so when it is
safe.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

net/sunrpc/sched.c

@@ -903,8 +903,10 @@ static void __rpc_execute(struct rpc_task *task)
 		/*
 		 * Lockless check for whether task is sleeping or not.
 		 */
-		if (!RPC_IS_QUEUED(task))
+		if (!RPC_IS_QUEUED(task)) {
+			cond_resched();
 			continue;
+		}
 
 		/*
 		 * Signalled tasks should exit rather than sleep.