Currently, qemu.conf is not tunable by OSA. However, the default
config file for qemu.conf is typically all comments and is
not frequently overwritten.
This patch enables deployers to deploy a custom /etc/libvirt/qemu.conf
config file by defining a dictionary qemu_conf_dict.
config_template plugin is not used because the qemu.conf file does
not have sections, thus putting values in [DEFAULT] is untested.
Change-Id: I780951ef466d1a82168f1f787abf58aebfe95889