[ATMOSPHERE-375] Enable Nova automatic host discovery at a set interval (#1749)

diff --git a/roles/nova/vars/main.yml b/roles/nova/vars/main.yml
index 3fe7294..0723353 100644
--- a/roles/nova/vars/main.yml
+++ b/roles/nova/vars/main.yml
@@ -108,6 +108,7 @@
         ovsdb_connection: unix:/run/openvswitch/db.sock
       scheduler:
         workers: 8
+        discover_hosts_in_cells_interval: 30
       vnc:
         auth_schemes: vencrypt,none
     nova_ironic: