clientIF: rescan devices on failed hotplugDisk

Change-Id: Ie5252a8ba6bf76c9eda3588c665ad379da3e9cfc
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=923773
Signed-off-by: Yeela Kaplan <ykaplan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/13454
Reviewed-by: Ayal Baron <abaron@redhat.com>