some docs are lost during rebalance in/out when queries are performed

Failing testcase:
viewquerytests.ViewQueryTests.test_employee_dataset_startkey_endkey_queries_rebalance_in,num_nodes:7
viewquerytests.ViewQueryTests.test_employee_dataset_alldocs_queries_rebalance_in,num_nodes:7
viewquerytests.ViewQueryTests.test_employee_dataset_startkey_endkey_queries_rebalance_out,num_nodes:7

jenkin's results: http://qa.hq.northscale.net/job/centos-64-vew-merge-tests/101/

steps in cases:
1. load data(Employee dataset is used: default bucket, 5 views)
2. add 6 node into cluster and starting rebalancing
3. during rebalancing perform queries

result: number of retrieved documents does not correspond to expected
AssertionError: ['None\n', 'Traceback (most recent call last):\n File "pytests/viewquerytests.py", line 401, in run_queries\n tc.assertEquals(num_keys, expected_num_docs, val)\nAssertionError: Query failed: 67120 Documents Retrieved, expected 67200\n', 'Traceback (most recent call last):\n File "pytests/viewquerytests.py", line 401, in run_queries\n tc.assertEquals(num_keys, expected_num_docs, val)\nAssertionError: Query failed: 67120 Documents Retrieved, expected 67200\n', 'Traceback (most recent call last):\n File "pytests/viewquerytests.py", line 401, in run_queries\n tc.assertEquals(num_keys, expected_num_docs, val)\nAssertionError: Query failed: 67125 Documents Retrieved, expected 67200\n', 'Traceback (most recent call last):\n File "pytests/viewquerytests.py", line 401, in run_queries\n tc.assertEquals(num_keys, expected_num_docs, val)\nAssertionError: Query failed: 67125 Documents Retrieved, expected 67200\n', 'Traceback (most recent call last):\n File "pytests/viewquerytests.py", line 401, in run_queries\n tc.assertEquals(num_keys, expected_num_docs, val)\nAssertionError: Query failed: 134247 Documents Retrieved, expected 134405\n']