Fix bug that caused RAID devices to be unable to activate if sub-LV was missing.

Fix bug that caused RAID devices to be unable to activate if sub-LV was missing.

Commit 02f6f4902fd90709f55e2e97e969ee28c2945c81 introduced a bug that caused
RAID devices to fail to activate if the device for a single sub-LV failed.
The special case of LVM mirror was handled, but not LVM RAID.
EXAMPLE:
[root@bp-01 ~]# devices vg
  LV            Copy%  Devices
  lv            100.00 lv_rimage_0(0),lv_rimage_1(0)
  [lv_rimage_0]        /dev/sde1(1)
  [lv_rimage_1]        /dev/sdh1(1)
  [lv_rmeta_0]         /dev/sde1(0)
  [lv_rmeta_1]         /dev/sdh1(0)
[root@bp-01 ~]# vgchange -an vg
  0 logical volume(s) in volume group "vg" now active
[root@bp-01 ~]# off.sh sdh
Turning off sdh
[root@bp-01 ~]# vgchange -ay vg --partial
  Partial mode. Incomplete logical volumes will be processed.
  Couldn't find device with uuid fbI0YO-GX7x-firU-Vy5o-vzwx-vAKZ-feRxfF.
  Cannot activate vg/lv_rimage_1: all segments missing.
  0 logical volume(s) in volume group "vg" now active

AFTER this patch:
[root@bp-01 ~]# vgchange -ay vg --partial
  Partial mode. Incomplete logical volumes will be processed.
  Couldn't find device with uuid fbI0YO-GX7x-firU-Vy5o-vzwx-vAKZ-feRxfF.
  1 logical volume(s) in volume group "vg" now active
[root@bp-01 ~]# devices vg
  Couldn't find device with uuid fbI0YO-GX7x-firU-Vy5o-vzwx-vAKZ-feRxfF.
  LV            Copy%  Devices
  lv            100.00 lv_rimage_0(0),lv_rimage_1(0)
  [lv_rimage_0]        /dev/sde1(1)
  [lv_rimage_1]        unknown device(1)
  [lv_rmeta_0]         /dev/sde1(0)
  [lv_rmeta_1]         unknown device(0)
[root@bp-01 ~]# dmsetup table vg-lv; dmsetup status vg-lv
0 1024000 raid raid1 3 0 region_size 1024 2 253:2 253:3 - -
0 1024000 raid raid1 2 AD 1024000/1024000

No WHATSNEW update necessary because this is an intrarelease fix.

 brassow