shared.unattended: Update the unattended files

Update the format of unattended files. Add some commands for
Windows test enviroment prepare. Also enlarge the Windows
image size to 30G as we will install more package inside the guests.

For the RHEL guests ks, we update some package that we needed. And
start X when guest booted up.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>