Description of problem:
Stream had I/O failure in debug info when destroy guest without graphic device,
and can't re-add graphic device .

Version-Release number of selected component (if applicable):
virt-manager-0.9.0-6.el6
libvirt-0.9.4-11.el6
python-virtinst-0.600.0-3.el6


How reproducible:
always

Steps to Reproduce:
1. Open virt-manager, make sure a good guest is in shutdown status

2. Open guest details page, Select Display VNC, Click Remove button, Finish

3. Start the guest

4. # virsh list --all
 Id Name                 State
----------------------------------
 23 win2008              running
the guest started without graphic device

5. Force off the guest,in debug info with error msg:

2011-09-19 03:03:58,729 (serialcon:150): Error receiving stream data
Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/serialcon.py", line 148, in _event_on_stream
    got = self.stream.recv(1024)
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 3541, in recv
    if ret == None: raise libvirtError ('virStreamRecv() failed')
libvirtError: stream had I/O failure
2011-09-19 03:03:58,731 (serialcon:208): Error finishing stream
Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/serialcon.py", line 206, in close
    self.stream.finish()
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 3393, in finish
    if ret == -1: raise libvirtError ('virStreamFinish() failed')
libvirtError: stream had I/O failure

6. switch to hardware detail page, add a vnc graphic to guest

7. start the guest.
the guest can start, but no vnc graphic shown in virt-manager.

Actual results:
see Steps to Reproduce

Expected results:
no error output when destroy guest without graphic device.
the guest can start normally with vnc graphic after re-add graphic device.


Additional info:
this issue occur on windows guest and rhel6 guest(installed X system)
if install rhel6 guest without X system, the guest can started with console normally.