Only pause in VMs when performing multinode testing

When we use a single VM, there is no need to wait extra
time for keyscan to complete. Add a flag to wait this
additional time when we perform multinode testing, such
as in DHCP test.

Change-Id: I10a54a91af145d6d44873865f5b7df48c68c59c7

playbooks/roles/bifrost-prepare-for-test-dynamic/defaults/main.yml

@@ -1,3 +1,4 @@
 ---
 node_ssh_pause: 10
 wait_timeout: 900
+multinode_testing: false

playbooks/roles/bifrost-prepare-for-test-dynamic/tasks/main.yml

@@ -27,6 +27,7 @@
   when: ipv4_address is defined
 - name: "Pause before asking for keyscan, to avoid races"
   pause: minutes=2
+  when: multinode_testing | bool == true
 - name: "Add testvm hosts from SSH known_hosts file."
   shell: ssh-keyscan "{{ ipv4_address }}" >> "{{ ansible_env.HOME }}/.ssh/known_hosts"
   when: ipv4_address is defined

playbooks/test-bifrost-dhcp.yaml

@@ -73,6 +73,7 @@
 - hosts: baremetal
   vars:
     inventory_dhcp_static_ip: "{{ inventory_dhcp_static_ip | bool }}"
+    multinode_testing: true
   name: "Creat configuration drive files and deploy machines."
   become: no
   connection: local