shard_existing.js failing across multiple linux 64-bit builds

assert: [40] != [41] are not equal : not right number of chunks

Error: Printing Stack Trace

    at printStackTrace (src/mongo/shell/utils.js:37:7)

    at doassert (src/mongo/shell/utils.js:58:1)

    at Function.assert.eq (src/mongo/shell/utils.js:88:1)

    at /data/buildslaves/Linux_RHEL_64bit/mongo/jstests/sharding/shard_existing.js:30:8

Sat Nov 17 09:13:33.006 exec error: src/mongo/shell/utils.js:59 [40] != [41] are not equal : not right number of chunks

throw msg;

      ^

failed to load: /data/buildslaves/Linux_RHEL_64bit/mongo/jstests/sharding/shard_existing.js