Also allow 3 concurrent runs of linux_release

Change-Id: I2d5dad00f3faa92cd362e984dbc3c8f005679699
diff --git a/infra/config/global/luci-scheduler.cfg b/infra/config/global/luci-scheduler.cfg
index ce9b979..f7f3305 100644
--- a/infra/config/global/luci-scheduler.cfg
+++ b/infra/config/global/luci-scheduler.cfg
@@ -441,6 +441,7 @@
   acl_sets: "default"
   triggering_policy: {
     max_batch_size: 1
+    max_concurrent_invocations: 3
   }
   buildbucket {
     server: "cr-buildbucket.appspot.com"