avocado.virt: Add option --disable-restore-image-job

Allow people to skip all uncompress guest image stages
if both --disable-restore-image-test and the new option,
--disable-restore-image-job are provided. If only the
former is provided, do the setup at plugin activation
stage. Print a 'Please wait...' message only if the
alternative output plugins (xunit and json) are not
claiming the application stdout.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>