We recently added support for VIR_DOMAIN_START_AUTODESTROY and
an impl to the QEMU driver. It is very desirable to support in
other drivers, so this adds it to LXC and UML

* src/lxc/lxc_conf.h, src/lxc/lxc_driver.c,
  src/uml/uml_conf.h, src/uml/uml_driver.c: Wire up autodestroy
  functions