Add default values for qemu max_files and max_proc

If qemu's max_proc / max_file are not defined in reclass, they
don't get defined, which causes qemu to fallback to system limits.

Related-PROD: PROD-35604
Change-Id: I3421ee2e66916203e8049e54bba1895a94c18c46
diff --git a/nova/compute/cluster.yml b/nova/compute/cluster.yml
index d6b0251..3b1587b 100644
--- a/nova/compute/cluster.yml
+++ b/nova/compute/cluster.yml
@@ -88,6 +88,9 @@
       # Set migration address explicitly to avoid such problems.
       libvirt:
         migration_inbound_addr: ${_param:single_address}
+      qemu:
+        max_processes: ${_param:qemu_max_processes}
+        max_files: ${_param:qemu_max_files}
       my_ip: ${_param:single_address}
       cache:
         security: