Set autoyast iso as 1st cdrom for url/nfs unattended_installation

For unattended_install.url and unattended_install.nfs,
autoyast.iso will be mounted as 1st cdrom.

Follow Paolo's suggestion, Add code to handle kernel_params
in unattended_install.py

Signed-off-by: Lin Ma <lma@suse.com>
Merge pull request #1502 from morecache/fix-cdrom-order-autoyast

Set autoyast iso as 1st cdrom for url/nfs unattended_installation