Report legacy bond devices instead of actually creating them

Engine <= 3.2 expects to see bonding devices bond0-bond4 predefined on
each host. Therefore, Vdsm creates them on boot, and never deletes them.
This add cumbersome logic, which has lead to bugs.

Instead, this patch simply reports the existence of the 5 expected
bonds, instead of actually creating them.

Note that bond0-bond4 were generated only on el6. Therefore this patch
limits the reports to that operating system.

Bug-Url: https://bugzilla.redhat.com/1064208
Change-Id: I4028a70cc8fd3e0599f02ac339a783a7d85f045e
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28455
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>