MINOR: task: Rename run_queue and run_queue_cur counters

<run_queue> is used to track the number of task in the run queue and
<run_queue_cur> is a copy used for the reporting purpose. These counters has
been renamed, respectively, <tasks_run_queue> and <tasks_run_queue_cur>. So the
naming is consistent between tasks and applets.

[wt: needed for next fixes, backport to 1.7 and 1.6]
diff --git a/src/haproxy.c b/src/haproxy.c
index b403ba1..c31ccb0 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1730,7 +1730,7 @@
 			break;
 
 		/* expire immediately if events are pending */
-		if (fd_cache_num || run_queue || signal_queue_len || applets_active_queue)
+		if (fd_cache_num || tasks_run_queue || signal_queue_len || applets_active_queue)
 			next = now_ms;
 
 		/* The poller will ensure it returns around <next> */