autotest/tp-libvirt — pull request #400 by PandaWei (2014-12-24 00:56:26+00:00)
Title: virsh_reboot.py: bugfix for qemu-ga

* some old linux version doesn't support qemu-ga command,
such as RHEL5.11.
* if there's a instance of qemu-guest-agent, executing the command
will encounter the following error,

output: '[root@localhost ~]#
1419277122.516774: critical: Cannot lock pid file,
Resource temporarily unavailable\n
1419277122.516788: critical: failed to create pidfile\n'

so it's better to do some check before qemu-ga is executed.