Skip non-virtual snapshots for availability

Skip non-virtual snapshots for availability

Change the behavior of availability change.
With this patch the lvgchange returns success
when VG is properly changed.

It skips non-virtual origins from being changes when
only 'vg' is specified as lvchange -a parameter.

Before this change we had this:

$> lvs -a
  LV    VG   Attr     LSize   Pool Origin
  lvol0 mvg  owi-a-s- 128.00k
  lvol1 mvg  owi-a-s- 128.00k
  lvol2 mvg  swi-a-s-   1.25m      lvol0
  lvol3 mvg  swi-a-s-   1.25m      lvol1

$> lvchange -an mvg ; echo $?
  Can't change snapshot logical volume "lvol2".
  Can't change snapshot logical volume "lvol3".
5

$> lvs -a
  LV    VG   Attr     LSize   Pool Origin
  lvol0 mvg  owi---s- 128.00k
  lvol1 mvg  owi---s- 128.00k
  lvol2 mvg  swi---s-   1.25m      lvol0
  lvol3 mvg  swi---s-   1.25m      lvol1

$> lvchange -ay mvg ; echo $?
  Can't change snapshot logical volume "lvol2".
  Can't change snapshot logical volume "lvol3".
5

$> lvs
  LV    VG   Attr     LSize   Pool Origin
  lvol0 mvg  owi-a-s- 128.00k
  lvol1 mvg  owi-a-s- 128.00k
  lvol2 mvg  swi-a-s-   1.25m      lvol0
  lvol3 mvg  swi-a-s-   1.25m      lvol1

After commit:

$> lvs -a
  LV    VG   Attr     LSize   Pool Origin
  lvol0 mvg  owi-a-s- 128.00k
  lvol1 mvg  owi-a-s- 128.00k
  lvol2 mvg  swi-a-s-   1.25m      lvol0
  lvol3 mvg  swi-a-s-   1.25m      lvol1

$> lvchange -an mvg ; echo $?
0

$> lvs -a
  LV    VG   Attr     LSize   Pool Origin
  lvol0 mvg  owi---s- 128.00k
  lvol1 mvg  owi---s- 128.00k
  lvol2 mvg  swi---s-   1.25m      lvol0
  lvol3 mvg  swi---s-   1.25m      lvol1

$> lvchange -ay mvg ; echo $?
0

$> lvs -a
  LV    VG   Attr     LSize   Pool Origin
  lvol0 mvg  owi-a-s- 128.00k
  lvol1 mvg  owi-a-s- 128.00k
  lvol2 mvg  swi-a-s-   1.25m      lvol0
  lvol3 mvg  swi-a-s-   1.25m      lvol1