lvremove: fix failed remove of all LVs in shared VG
    
    commit a125a3bb505cc "lv_remove: reduce commits for removed LVs"
    changed "lvremove <vgname>" from removing one LV at a time,
    to removing all LVs in one vg write/commit.  It also changed
    the behavior if some of the LVs could not be removed, from
    removing those LVs that could be removed, to removing nothing
    if any LV could not be removed.  This caused a regression in
    shared VGs using sanlock, in which the on-disk lease was
    removed for any LV that could be removed, even if the command
    decided to remove nothing.  This would leave LVs without a
    valid ondisk lease, and "lock failed: error -221" would be
    returned for any command attempting to lock the LV.
    
    Fix this by not freeing the on-disk leases until after the
    command has decided to go ahead and remove everything, and
    has written the VG metadata.
    
    Before the fix:
    
    node1: lvchange -ay vg/lv1
    node2: lvchange -ay vg/lv2
    
    node1: lvs
      lv1  test -wi-a----- 4.00m
      lv2  test -wi------- 4.00m
    node2: lvs
      lv1  test -wi------- 4.00m
      lv2  test -wi-a----- 4.00m
    
    node1: lvremove -y vg/lv1 vg/lv2
      LV locked by other host: vg/lv2
    
    (lvremove removed neither of the LVs, but it freed
    the lock for lv1, which could have been removed
    except for the proper locking failure on lv2.)
    
    node1: lvs
      lv1  test -wi------- 4.00m
      lv2  test -wi------- 4.00m
    
    node1: lvremove -y vg/lv1
    LV vg/lv1 lock failed: error -221
    
    (The lock for lv1 is gone, so nothing can be done with it.)