[system test] rebalance hang when add nodes to cluster

Cluster information:
- 8 centos 6.2 64bit server with 4 cores CPU
- Each server has 32 GB RAM and 400 GB SSD disk.
- SSD disk format ext4 on /data
- Each server has its own drive, no disk sharing with other server.
- Load 15 million items to both buckets
- Cluster has 2 buckets, default (11GB) and saslbucket (11GB) with consistent view enable. For 2 buckets, we use only 68% total RAM of system.
- Each bucket has one doc and 2 views for each doc (default d1 and saslbucket d11)

* Create cluster with 4 nodes installed couchbase server 2.0.0-1746

10.6.2.37
10.6.2.38
10.6.2.39
10.6.2.40

* Data path /data
* View path /data

* Add 4 nodes to cluster and rebalance
10.6.2.42
10.6.2.43
10.6.2.44
10.6.2.45

* rebalance hang

* Link to collect info of all nodes https://s3.amazonaws.com/packages.couchbase/collect_info/orange/2_0_0/201209/8nodes-col-info-1746-reb-hang-20120920.tgz

Link to atop file of all nodes https://s3.amazonaws.com/packages.couchbase/atop-files/orange/201209/atop-8nodes-1746-reb-hang-20120920.tgz