Fix DHCP test scenario

It appears that test nodes, once are explicitly powered off,
depending on libvirt, may completely vanish. As we only test
at the end of the process if we've observed additional DHCP
leases, we should move to only defining the VMs such that they
are powered on when the sequence is ready, not in advance of
the test sequence.

Moving to defining instead of creating does improve the overall
efficency of the sequence as no processes are spawning suddenly
using CPU and RAM during the start of the test. This also allows
us to remove and correct ansible virt module invocations.

The ansible virt module is an extra module, not a core module,
at least on Ubuntu Trusty, cannot have it's requirements installed
via pip.

Change-Id: I8948ba5a941384fdcacebcdfe9b6fd4fe8384cb1
Depends-On: I01885c397ed1e020aae306db1656678b26306532

playbooks/roles/bifrost-create-vm-nodes/files/create_vm_nodes-for-role.sh

@@ -197,7 +197,9 @@ function create_node {
 "
 
       echo ${vm_xml} > /tmp/vm.xml
-      virsh create /tmp/vm.xml 2>&1 >/dev/null
+      # NOTE(TheJulia): the create command powers on a VM that has been defined,
+      # where as define creates the VM, but does not change the power state.
+      virsh define /tmp/vm.xml 2>&1 >/dev/null
       if [ $? != 0 ]
       then
          echo "failed to create VM $NAME" >&2

playbooks/test-bifrost.yaml

@@ -16,13 +16,6 @@
     # in the interest of keeping the active memory footprint small,
     # should stop all of the VMs in advance, so we can proceed with
     # install and initial deploy.
-  - name: Attempt to stop all test VMs
-    virt:
-      name: "testvm{{ item }}"
-      command: "stop"
-      state: shutdown
-    with_sequence: start=1 end={{ test_vm_num_nodes | default('5') }}
-    ignore_errors: yes
   - name: Remove pre-existing leases file
     file: path=/var/lib/misc/dnsmasq.leases state=absent
 - hosts: localhost
@@ -129,9 +122,7 @@
     # validate that the dhcp config is working as expected and not
     # serving these requests.
   - name: Power on remaining test VMs
-    virt:
-      name: "testvm{{ item }}"
-      command: "start"
+    command: virsh start testvm{{item}}
     with_sequence: start=4 end={{ test_vm_num_nodes | default('5') }}
     ignore_errors: yes
     when: inventory_dhcp | bool == true