BUG/MINOR, BUG/MINOR: lua: Put tasks to sleep when waiting for data

If a lua socket is waiting for data it currently spins at 100% cpu usage.
This because the TICK_ETERNITY returned by the socket is ignored when
setting the 'expire' time of the task.

Fixed by removing the check for yields that return TICK_ETERNITY.

This should be backported to at least 1.8.
diff --git a/src/hlua.c b/src/hlua.c
index 32199c9..4c56409 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -5552,8 +5552,7 @@
 
 	case HLUA_E_AGAIN: /* co process or timeout wake me later. */
 		notification_gc(&hlua->com);
-		if (hlua->wake_time != TICK_ETERNITY)
-			task->expire = hlua->wake_time;
+		task->expire = hlua->wake_time;
 		break;
 
 	/* finished with error. */