Add (debug ...) command to enable logging from inside the policy

Change-Id: I23dae405908a4d801dc9ac28a9fe2caff698f603
Signed-off-by: Martin Sivak <msivak@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/21725
Reviewed-by: Adam Litke <alitke@redhat.com>
Tested-by: Adam Litke <alitke@redhat.com>