qga: drop guest_file_init helper and replace it with static initializers

This just makes code shorter and better.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Yuri Pudgorodskiy <yur@virtuozzo.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
