CBQE-158: memcapable.AppendTests.test_append_with_delete broken

Change-Id: I46927128d4e18399a6084ca1f4a1da96e20e6f98
Reviewed-on: http://review.couchbase.org/23912
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>