Bug 750724

Description of problem:
Add a 'dir' storage, use '/home/test/' as target path . After pool was added succuessfully. select it, and quickly double-click "Refresh volume list" Button for several times, virt-manager will exit or the host screen is frozen(sometimes it could be reproduced),only the mouse could be moved, and the host needed to be reboot.
When there are many volumes in the storage, this problem could be easily reproduced. 

Version-Release number of selected component (if applicable):
kernel-2.6.32-207.el6.x86_64
libvirt-0.9.4-19.el6.x86_64
qemu-kvm-0.12.1.2-2.196.el6.x86_64
python-virtinst-0.600.0-5.el6.noarch
virt-manager-0.9.0-7.el6.x86_64

How reproducible:
Almost

Steps to Reproduce:
1. #virt-manager --debug
2. add a 'dir' storage, name is "home", target path is "/home/test"( should be changed if your computer's normal user is not test). click finish.
3. Ｓelect the added storage. and quickly double-click "Refresh volume list" Button for several times(about 10 times or so.)
4. then the virt-manager will exit or the host screen is frozen(sometimes it could be reproduced).
  
Actual results:
see the attachments. 

Expected results:
There should be no error.

Additional info: