Fix select menu data append

Select menu appended data to list,
this results in items accumulating when everytime try to set data.
Fix it by clear list before appending.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
UI: Support add guest disk

Extend current cdrom disk add to cdrom disk attachment.
Also add 'bus' for user to choose from.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Display all disk types in storage edit view

Instead of just displaying cdrom type in storage edit view,
Add disk type to storage display view to make sure
we get the right view after attach and detach new disk.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>