MINOR: checks: add a new global max-spread-checks directive

This directive ensures that checks with a huge interval do not start
too far apart at the beginning.
diff --git a/src/checks.c b/src/checks.c
index 24b763d..fceb2c7 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -1744,11 +1744,14 @@
 	t->process = process_chk;
 	t->context = check;
 
+	if (mininter < srv_getinter(check))
+		mininter = srv_getinter(check);
+
+	if (global.max_spread_checks && mininter > global.max_spread_checks)
+		mininter = global.max_spread_checks;
+
 	/* check this every ms */
-	t->expire = tick_add(now_ms,
-			     MS_TO_TICKS(((mininter &&
-					   mininter >= srv_getinter(check)) ?
-					  mininter : srv_getinter(check)) * srvpos / nbcheck));
+	t->expire = tick_add(now_ms, MS_TO_TICKS(mininter * srvpos / nbcheck));
 	check->start = now;
 	task_queue(t);