libvirt.get_started: Added non-interactive option

* Added option —-non-interactive to disable yes/no prompt and suppress
  verbose output.

* Added option —-setup-selinux to force setup SELinux contexts for
  shared/data directory and restore them to defaults.

When running libvirt.get_started from scripts such as CI.  It is necessary
to make it non-interactive and keep things under control by using options.

Signed-off-by: Hao Liu <hliu@redhat.com>
Merge pull request #1146 from Hao-Liu/non_interactive

libvirt.get_started: Added non-interactive option