Image: Add run function
Image: Add run function

Run an already-built template
If there is no execution command specified by user, source.get_command will
find the command to invoke

Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

libvirt/libvirt-sandbox,libvirt/libvirt-sandbox,agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian,libvirt/libvirt-sandbox,agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian