Merge changes from topic "no-instance-flag" into gce-dev

* changes:
  Refactors libvirt dependencies out of guest_config and launcher
  Replaces -instance flag with CUTTLEFISH_INSTANCE environment variable
tree: 96b551d759124e543ce0e1c2a36e348257a4d9e3
  1. common/
  2. guest/
  3. host/
  4. tests/
  5. tools/
  6. Android.bp
  7. Android.mk
  8. OWNERS