On the very first log message we send to any output, we include
the libvirt version number and package string. In some bug reports
we have been given libvirtd.log files that came from a different
host than the corresponding /var/log/libvirt/qemu log files. So
extend the initial log message to include the hostname too.

eg on first log message we would now see:

 $ libvirtd
 2015-12-04 17:35:36.610+0000: 20917: info : libvirt version: 1.3.0
 2015-12-04 17:35:36.610+0000: 20917: info : hostname: dhcp-1-180.lcy.redhat.com
 2015-12-04 17:35:36.610+0000: 20917: error : qemuMonitorIO:687 : internal error: End of file from monitor
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>