RHEV host was fenced, with the messages "WARNING connection to libvirt broken" and "CRITICAL taking calling process down" reported by VDSM

Issue

• RHEV host crashed.

• RHEV host was fenced with messages as below:

Nov 19 08:32:26 xxxxx vdsm root WARNING connection to libvirt broken. ecode: 1 edom: 7
Nov 19 08:32:26 xxxxx vdsm root CRITICAL taking calling process down.
Nov 19 08:32:26 xxxxx vdsm vm.Vm ERROR vmId=`5327abea-fe95-498a-92a0-5407b04a1ebe`::Stats function failed: <AdvancedStatsFunction _sampleBalloon at 0x2e22650>#012
Traceback (most recent call last):#012  
File "/usr/share/vdsm/sampling.py", line 396, in collect#012  
File "/usr/share/vdsm/sampling.py", line 271, in __call__#012  
File "/usr/share/vdsm/vm.py", line 611, in _sampleBalloon#012  
File "/usr/share/vdsm/vm.py", line 928, in f#012  
File "/usr/lib64/python2.6/site-packages/vdsm/libvirtconnection.py", line 110, in wrapper#012  
File "/usr/lib64/python2.6/site-packages/libvirt.py", line 3389, in getLibVersion#012
libvirtError: internal error client socket is closed