Remove unused configurations

The following configurations are not used.

o host_state_interval=120
    This configuration was added in the following commit.

      commit 6e6b4ad411cae3918cd2b54152c52fe3932dd723
      Author: Gary Kotton <gkotton@vmware.com>
      Date:   Wed Dec 4 05:36:21 2013 -0800

          Image cache: move all of the variables to a common place

    But it can not be seen to be using to me.

o lvm_snapshot_size=1000
    This configuration was renamed from 'libvirt_lvm_snapshot_size'
    in the following commit.

      commit 25a7de2054ba6ae5eb318c86fe165f4302fbfff8
      Author: Michael Still <mikal@stillhq.com>
      Date:   Wed Nov 6 15:25:05 2013 +1100

          Move flags in libvirt's imagebackend to the libvirt group

    'libvirt_lvm_snapshot_size' was removed in the following commit.

      commit 8c985874c7885f31871204d3f83ce547fefc5fb6
      Author: Vladan Popovic <vpopovic@redhat.com>
      Date:   Thu Oct 17 07:41:20 2013 -0400

          Remove unnecessary steps for cold snapshots

Change-Id: Ic2b45a3330769ab7c3c5a92ea38bd9d0f9ef519a
Merge "Remove unused configurations"