fix NoMethodError in ShellOut run_command

Traceback:

================================================================================
Recipe Compile Error in /root/chef-solo/cookbooks-2/openstack-compute/recipes/compute.rb
================================================================================

NoMethodError
-------------
undefined method `error' for #<Mixlib::ShellOut:0x0000000340f878>

Cookbook Trace:
---------------
  /root/chef-solo/cookbooks-2/openstack-compute/recipes/libvirt.rb:62:in `set_grub2_default_
kernel'
  /root/chef-solo/cookbooks-2/openstack-compute/recipes/libvirt.rb:75:in `set_boot_kernel_an
d_trigger_reboot'
  /root/chef-solo/cookbooks-2/openstack-compute/recipes/libvirt.rb:102:in `from_file'
  /root/chef-solo/cookbooks-2/openstack-compute/recipes/compute.rb:78:in `from_file'

Relevant File Content:
----------------------
/root/chef-solo/cookbooks-2/openstack-compute/recipes/libvirt.rb:

 55:      ::Chef::Log.info("Changed grub default to #{default_boot}")
 56:      Mixlib::ShellOut.new("sed -i -e \"s;^default.*;default #{default_boot};\" /boot/gr
ub/menu.lst").run_command
 57:    end
 58:  end
 59:
 60:  def set_grub2_default_kernel(flavor='default')
 61:    boot_entry = "'openSUSE GNU/Linux, with Xen hypervisor'"
 62>>   if Mixlib::ShellOut.new("grub2-set-default #{boot_entry}").error
 63:      ::Chef::Application.fatal!(
 64:        "Unable to change grub2 default to #{boot_entry}")
 65:    else
 66:      ::Chef::Log.info("Changed grub2 default to #{boot_entry}")
 67:    end
 68:  end
 69:
 70:  def set_boot_kernel_and_trigger_reboot(flavor='default')
 71:    # only default and xen flavor is supported by this helper right now

Change-Id: If4b3426bd1b989a94bcdf9d6b221fdb0c1b8da91
Merge "fix NoMethodError in ShellOut run_command"