Description of problem:
When virsh -r <subcommand> fails to connect to the hypervisor, and virsh plugin is enabled in sosreport, then it produces backtrace:

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/sos/sosreport.py", line 1252, in setup
    plug.setup()
  File "/usr/lib/python2.7/site-packages/sos/plugins/virsh.py", line 59, in setup
    pos = k_lines[0].split().index('Name')
ValueError: 'Name' is not in list

Reason:
 53         for k in ['net', 'nwfilter', 'pool']:
 54             self.add_cmd_output('%s %s-list' % (cmd, k))
 55             k_file = self.get_cmd_output_now('%s %s-list' % (cmd, k))
 56             if k_file:
 57                 k_lines = open(k_file, 'r').read().splitlines()
 58                 # the 'name' column position changes between virsh cmds
 59                 pos = k_lines[0].split().index('Name')

cmd on line 54 calls virsh that returns the failure:

['error: failed to connect to the hypervisor', "error: Failed to connect socket to '/var/run/libvirt/libvirt-sock-ro': No such file or directory", '']

that does not contain 'Name' substring either where.


Version-Release number of selected component (if applicable):
sos-3.4-2.el7.noarch


How reproducible:
100%


Steps to Reproduce:
1. Switch off libvirt hypervisor / in some other means, cause the "virsh -r net-list" command generates the above error.
2. sosreport --batch -o virsh


Actual results:
caught exception in plugin method "virsh.setup()"
writing traceback to sos_logs/virsh-plugin-errors.txt
..
and the virsh-plugin-errors.txt has:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/sos/sosreport.py", line 1252, in setup
    plug.setup()
  File "/usr/lib/python2.7/site-packages/sos/plugins/virsh.py", line 59, in setup
    pos = k_lines[0].split().index('Name')
ValueError: 'Name' is not in list


Expected results:
no such error


Additional info: