openqa-clone-job: Apply group settings to all cloned jobs

This change makes `_GROUP` and `_GROUP_ID` "global" settings so
one can clone a set of jobs into another group or no group via,
e.g. `openqa-clone-job $some_url _GROUP=0`. Otherwise one needed
to take dependencies into account and possibly specify
`--parental-inheritance` (which would then apply all settings to
the parent which might not be wanted as well).

The downside is that leaving the parent jobs that are cloned as
well in their job groups is not possible anymore. However, I
don't think that this is a realy use case of our users anyways.

lib/OpenQA/Script/CloneJob.pm

@@ -25,7 +25,7 @@ our @EXPORT = qw(
   post_jobs
 );
 
-use constant GLOBAL_SETTINGS => ('WORKER_CLASS');
+use constant GLOBAL_SETTINGS => (qw(WORKER_CLASS _GROUP _GROUP_ID));
 
 use constant JOB_SETTING_OVERRIDES => {
     _GROUP => '_GROUP_ID',