Delete 'bus' param from backend

Since we pick the best bus type according to distro/version/arch
when creating template instead of giving users choice,
this logic can be applied to add vm disk logic.
So delete 'bus' param from api and let kimchi decide the best bus type
to use.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Delete 'bus' selection from UI

Do not expose 'bus' selection in UI and let kimchi choose for them.

Signed-off-by: Royce Lv <lvroyce@linux.vnet.ibm.com>
Update testcases for bus type decision making

Test kimchi will find right type of bus when attaching disks,
update test for ide bus does not support hot plug.

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