cluster/stripe: don't treat ESTALE as failure in lookup

Backport of: http://review.gluster.org/8135

Problem:
In a stripe volume, symlinks are created only on the first brick via the
default_symlink() call. During gfid lookup, server sends ESTALE from the other
bricks, which is treated as error in stripe_lookup_cbk()

Fix:
Don't treat ESTALE as error in stripe_lookup_cbk()

BUG: 1111454
Change-Id: I337ef847f007b7c20feb365da329c79c121d20c4
Signed-off-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-on: http://review.gluster.org/8153
Reviewed-by: Raghavendra Bhat <raghavendra@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Niels de Vos <ndevos@redhat.com>