cluster/dht: handle ESTALE appropriately in rmdir codepath.

Till we separated the scenario of a file/directory not existing from
parent not existing [1], we used to include a subvolume in the layout
of a directory even if it is not present on that subvolume. This was
done to allow a lookup racing with mkdir to create correct layout.
However, there are other scenarios as well where a directory is not
present. One such situation is trying to create a directory after an
add-brick. Since there is no guarantee that all the ancestors are
created after an add-brick (and hence directory cannot be created), the
newly added brick should not be part of the layout. However, we used to
consider newly added brick as part of layout (even before we do
fix-layout of all the ancestors) and this was the root cause of [2].
With [1], this issue got fixed and hence [2] got fixed too. However,
[1] is not complete in the sense we didn't modify rmdir codepath
appropriately. This patch fixes that gap.

[1] http://review.gluster.org/6322
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1006809

Change-Id: I79ab96bb8abb6f3d90bb6e235a1c465e1be0fd19
BUG: 1032894
Signed-off-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-on: http://review.gluster.org/8142
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>