Description of problem:

during live snapshot testing, i'v hit a case where i managed somehow to run createVolume from hsm host, and got the following: 

Thread-671::ERROR::2011-12-21 13:07:48,128::task::855::TaskManager.Task::(_setError) Task=`12292bf9-1578-4acd-a814-7c799392dff1`::Unexpected error
 Traceback (most recent call last):
   File "/usr/share/vdsm/storage/task.py", line 863, in _run
     return fn(*args, **kargs)
   File "/usr/share/vdsm/logUtils.py", line 38, in wrapper
     res = f(*args, **kwargs)
   File "/usr/share/vdsm/storage/hsm.py", line 1097, in public_createVolume
     srcImgUUID, srcVolUUID
   File "/usr/share/vdsm/storage/hsm.py", line 544, in _spmSchedule
     self.taskMng.scheduleJob("spm", pool.tasksDir, vars.task, name, func, *args)
 AttributeError: 'setMaxHostID' object has no attribute 'tasksDir'

createVolume should only be executed on SPM machine, the actual error here is wrong, and command should be blocked before it reaches that point. 

git commit: 67800f45d6c776a9964327429ff6ddc8feea353a

repro:

execute create volume task on HSM using vdsClient.