ui: add a vm load icon for multi-click bug.

The vm power-up icon is green.
The vm load icon is gray.
The vm power-down icon is red.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Signed-off-by: Bing Bu Cao <mars@linux.vnet.ibm.com>
ui: overwrite vm start and stop click event to fix multi-click bug.

when click the 'start' or 'stop' button, the button will be locked until
ajax executed successfully.

Signed-off-by: ShaoHe Feng <shaohef@linux.vnet.ibm.com>
Signed-off-by: Bing Bu Cao <mars@linux.vnet.ibm.com>