Add Ironic sideways migration testing

This adds the ability for grenade to be used to run a 'sideways'
upgrade within the Juno release to migrate nodes from Nova Baremetal
to Ironic.  The process is as follows:

  * Deploy base Nova with VIRT_DRIVER=fake, stop base.
  * Deploy target with VIRT_DRIVER=ironic
  * Create Nova baremetal nodes and interfaces in db that map to
    VMs
  * Run Ironic migration scripts to migrate Nova baremetal nodes and
    interfaces to Ironic
  * Update baremetal flavor to reference Ironic deployment ramdisk
    and kernel
  * Run smoke tests against target

Change-Id: Icca6ed4d304c5177a8e41db14c85354d73f10edf