UI: refactor guest edit code.

We don not need a special "save" button for permission form.

All form in guest edit tab can share the same "save" button.

also, we will add a password form, it will also share this button.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Signed-off-by: Simon Jin <simonjin@linux.vnet.ibm.com>