adding new node to cluster while rebalance is running causes rebalance to fail with detected_nodes_change condition

build-1666
steps:
1. node in cluster - 10.3.121.92
2. rebalance in 10.5.2.11 and start rebalance
3. when rebalance is in progress from api initialize new rebalance with params:

password=password&ejectedNodes=&user=Administrator&knownNodes=ns_1%4010.3.121.93%2Cns_1%4010.3.121.94%2Cns_1%4010.5.2.11%2Cns_1%4010.3.121.92%2Cns_1%4010.3.121.95

as a result the first rebalance is failed:

Rebalance exited with reason {detected_nodes_change,
{ns_node_disco_events,
['ns_1@10.3.121.92','ns_1@10.5.2.11'],
['ns_1@10.3.121.92','ns_1@10.3.121.93',
'ns_1@10.5.2.11']}}

[error_logger:error,2012-08-31T12:27:47.902,ns_1@10.3.121.92:error_logger:ale_error_logger_handler:log_report:72]
=========================CRASH REPORT=========================
crasher:
initial call: ns_vbucket_mover:init/1
pid: <0.31823.0>
registered_name: []
exception exit: {detected_nodes_change,
{ns_node_disco_events,
['ns_1@10.3.121.92','ns_1@10.5.2.11'],
['ns_1@10.3.121.92','ns_1@10.3.121.93',
'ns_1@10.5.2.11']}}
in function gen_server:terminate/6
ancestors: [<0.31774.0>]
messages: [{'EXIT',<0.936.1>,
{detected_nodes_change,

{ns_node_disco_events, ['ns_1@10.3.121.92','ns_1@10.5.2.11'], ['ns_1@10.3.121.92','ns_1@10.3.121.93', 'ns_1@10.5.2.11']}

}}]
links: [<0.31774.0>,<0.31827.0>,<0.57.0>]
dictionary: [

{bucket_name,"standard_bucket0"}

,

{i_am_master_mover,true}

,

{child_processes,[<0.936.1>,<0.878.1>,<0.833.1>,<0.800.1>, <0.763.1>,<0.727.1>,<0.693.1>,<0.650.1>, <0.614.1>,<0.581.1>,<0.547.1>,<0.511.1>, <0.478.1>,<0.448.1>,<0.427.1>,<0.406.1>, <0.385.1>,<0.364.1>,<0.340.1>,<0.319.1>, <0.298.1>,<0.275.1>,<0.248.1>,<0.227.1>, <0.206.1>,<0.185.1>,<0.164.1>,<0.143.1>, <0.122.1>,<0.101.1>,<0.77.1>,<0.56.1>, <0.35.1>,<0.14.1>,<0.32761.0>,<0.32740.0>, <0.32719.0>,<0.32698.0>,<0.32677.0>, <0.32656.0>,<0.32635.0>,<0.32614.0>, <0.32593.0>,<0.32568.0>,<0.32547.0>, <0.32526.0>,<0.32505.0>,<0.32483.0>, <0.32461.0>,<0.32435.0>,<0.32414.0>, <0.32390.0>,<0.32369.0>,<0.32348.0>, <0.32326.0>,<0.32305.0>,<0.32284.0>, <0.32259.0>,<0.32235.0>,<0.32214.0>, <0.32193.0>,<0.32172.0>,<0.32148.0>, <0.32127.0>,<0.32106.0>,<0.32085.0>, <0.32064.0>,<0.32043.0>,<0.32022.0>, <0.32001.0>,<0.31980.0>,<0.31959.0>, <0.31937.0>,<0.31916.0>,<0.31895.0>, <0.31871.0>,<0.31850.0>,<0.31829.0>]}

]
trap_exit: true
status: running
heap_size: 6765
stack_size: 24
reductions: 609293
neighbours:
neighbour: [

{pid,<0.31774.0>}

,

{registered_name,[]}

,
{initial_call,{erlang,apply,2}},
{current_function,{ns_rebalancer,wait_for_mover_tail,2}},

{ancestors,[]}

,

{messages,[]}

,

{links,[<0.31291.0>,<0.31823.0>]}

,
{dictionary,[{random_seed,{8712,26823,9965}}]},

{trap_exit,false}

,

{status,waiting}

,

{heap_size,28657}

,

{stack_size,28}

,

{reductions,175181}

]