Ensure 'unitfile' attribute is always present
Ensure 'unitfile' attribute is always present

In the SystemdContainer class, make sure that the 'unitfile'
attribute is always set in the constructor, so later methods
can rely on it.

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

agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian,libvirt/libvirt-sandbox,gczarcinski/libvirt-sandbox,gczarcinski/libvirt-sandbox,libvirt/libvirt-sandbox,erenyagdiran/libvirt-sandbox,gczarcinski/libvirt-sandbox,gczarcinski/libvirt-sandbox,gczarcinski/libvirt-sandbox,erenyagdiran/libvirt-sandbox,gczarcinski/libvirt-sandbox,erenyagdiran/libvirt-sandbox,agx/libvirt-sandbox-debian,agx/libvirt-sandbox-debian,libvirt/libvirt-sandbox,agx/libvirt-sandbox-debian,erenyagdiran/libvirt-sandbox