sampling: live merge: avoid wasteful picklecopy

The Vm.queryBlockJobs() API always return a fresh dictionary,
so it is safe to copy it directly, saving a picklecopy.

Change-Id: I1b23e42f14f9d334734ee1c77c9d11c33afe5aec
Signed-off-by: Francesco Romani <fromani@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/35621
Reviewed-by: Adam Litke <alitke@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>