commit 4c7e3093 upstream.

redistribute3() shares entries out across 3 nodes.  Some entries were
being moved the wrong way, breaking the ordering.  This manifested as a
BUG() in dm-btree-remove.c:shift() when entries were removed from the
btree.

For additional context see:
https://www.redhat.com/archives/dm-devel/2015-May/msg00113.htmlSigned-off-by: Dennis Yang <shinrairis@gmail.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>