virttest: escape character to avoid error when get qemu help info

replace '?' with '\\?' to avoid get qemu help message error in shell;

Signed-off-by: Xu Tian <xutian@redhat.com>
shared.unattended: update ubuntu preseed

add 'lvm2' and 'ethtool' packages in preseed, because it requried to 'ethtool'
and 'lvm' tests;

Signed-off-by: Xu Tian <xutian@redhat.com>