core: audit log - use hypervisor and not ovirt-node

When adding a hypervisor through the host the manager audit log should
state "Host is hypervisor" and not "Host is ovirt-node" because the term
hypervisor includes both ovirt-node and rhevh.

Change-Id: Ie0dbe402c6c1fa1b5a01af30e4bbb320e12b11d5
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=921070
Signed-off-by: Mooli Tayer <mtayer@redhat.com>