Description of problem:

When migrating multiple VMs some getting stuck in Paused status on the source host. 

vdsm log:

Thread-612::ERROR::2011-01-24 13:05:41,728::vm::453::vds.vmlog.67cd8b9a-f684-46d2-b2a0-c7fa62b4fe3f::(run) Traceback (most recent call last):
  File "/usr/share/vdsm/vm.py", line 446, in run
    self._finishSuccessfully()
  File "/usr/share/vdsm/vm.py", line 373, in _finishSuccessfully
    self._vm.setDownStatus(NORMAL, "Migration succeeded")
  File "/usr/share/vdsm/vm.py", line 1743, in setDownStatus
    self.lastStatus = 'Down'
  File "/usr/share/vdsm/vm.py", line 576, in _set_lastStatus
    self.saveState()
  File "/usr/share/vdsm/libvirtvm.py", line 918, in saveState
    vm.Vm.saveState(self)
  File "/usr/share/vdsm/vm.py", line 1227, in saveState
    pickle.dump(toSave, f)
  File "/usr/lib64/python2.6/pickle.py", line 1362, in dump
    Pickler(file, protocol).dump(obj)
  File "/usr/lib64/python2.6/pickle.py", line 224, in dump
    self.save(obj)
  File "/usr/lib64/python2.6/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib64/python2.6/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib64/python2.6/pickle.py", line 663, in _batch_setitems
    save(v)
  File "/usr/lib64/python2.6/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib64/python2.6/pickle.py", line 600, in save_list
    self._batch_appends(iter(obj))
  File "/usr/lib64/python2.6/pickle.py", line 615, in _batch_appends
    save(x)
  File "/usr/lib64/python2.6/pickle.py", line 286, in save
    f(self, obj) # Call unbound method with explicit self
  File "/usr/lib64/python2.6/pickle.py", line 649, in save_dict
    self._batch_setitems(obj.iteritems())
  File "/usr/lib64/python2.6/pickle.py", line 661, in _batch_setitems
    for k, v in items:
RuntimeError: dictionary changed size during iteration

Versions:
-rhel 6.1 based hosts
-vdsm-4.9-43.1
-libvirt-0.8.7-3
-rhevm 2.3

repo steps:

1) Create 30 VMs from pool.
2) Migrate all of them together from one host to another.