Use a mirrored mirror log

By default, LVM will sync the two mirrors of a logical volume on
creation. This is I/O intensive and it takes a long time though, so we
tell it not to with --nosync. The next default behavior is to create a
mirror log which says what portions of the mirrors are in sync. But
then if a disk backing a mirror log fails, we have to deal with
resyncing the mirrors at each reboot.

This commit tells LVM to use a mirrored mirror log, which will use
approximately 4MB of extra space, but means we'll never have to
sync mirrors, ever.

Change-Id: I6586ced4e7e66ae79ae134406a4c633f8fbc8602
Remove unused config options

The following options are not used.

o fake_tests=true
  This configuration was removed in the following commit.

    commit 6ae520677da80103bae79e3db3569360df1220cd
    Author: Monty Taylor <mordred@inaugust.com>
    Date:   Fri May 24 01:36:21 2013 +0200

        Replace custom skip_ methods.

o backlog=4096
  This configuration was added in the following commit.

    commit 24d961023f2a32ca3454991a7891199d2da796dc
    Author: Davanum Srinivas <dims@linux.vnet.ibm.com>
    Date:   Sat Jan 12 16:16:19 2013 -0500

        Support for SSL in wsgi.Server

  But there is no evidence that was used.

o bindir=$pybasedir/bin
  This configuration was added in the following commit.

    commit c53d8e343e50d4cf7ea9a6a81258848c2d893bfb
    Author: Jenkins <jenkins@review.openstack.org>
    Date:   Thu May 3 10:48:26 2012 -0700

        Initial fork out of Nova.

  But there is no evidence that was used.

o root_helper=sudo
  This configuration was removed in the following commit.

    commit 5bce6ad46f57d22fcb22ba9e194fbd1e2d53f55d
    Author: John Griffith <john.griffith@solidfire.com>
    Date:   Tue Jun 4 17:07:03 2013 -0600

        Use common.processutils.execute

o nexenta_mount_options=<None>
  This configuration was added in the following commit.

    commit 96677735f6d8f1f5b6380127956921f719aab799
    Author: Mikhail Khodos <hodosmb@gmail.com>
    Date:   Wed Aug 14 11:18:12 2013 -0700

        Adds Nexenta NFS driver

  But there is no evidence that was used.

o nexenta_used_ratio=0.95
  This configuration was added in the following commit.

    commit 96677735f6d8f1f5b6380127956921f719aab799
    Author: Mikhail Khodos <hodosmb@gmail.com>
    Date:   Wed Aug 14 11:18:12 2013 -0700

        Adds Nexenta NFS driver

  But there is no evidence that was used.

o nexenta_oversub_ratio=1.0
  This configuration was added in the following commit.

    commit 96677735f6d8f1f5b6380127956921f719aab799
    Author: Mikhail Khodos <hodosmb@gmail.com>
    Date:   Wed Aug 14 11:18:12 2013 -0700

        Adds Nexenta NFS driver

  But there is no evidence that was used.

o zadara_default_striping_mode=simple
  This configuration was removed in the following commit.

    commit 2f907133aeaee09f58be30e75089c23b13573500
    Author: Vladimir Popovski <vladimir@zadarastorage.com>
    Date:   Fri Aug 16 04:34:54 2013 +0000

        Add features to Zadara Storage Cinder driver

o zadara_default_stripesize=64
  This configuration was removed in the following commit.

    commit 2f907133aeaee09f58be30e75089c23b13573500
    Author: Vladimir Popovski <vladimir@zadarastorage.com>
    Date:   Fri Aug 16 04:34:54 2013 +0000

        Add features to Zadara Storage Cinder driver

Change-Id: Ie78b8c7fc081899b8053060150e81e1a6c5d4958
Merge "Remove unused config options"
Merge "Use a mirrored mirror log"