webadmin: When adding a new VM disk, allow activation in certain VM statuses

When adding a disk to a VM, allow disk activation only for a VM in status
Up/Down/Paused otherwise the CDA in the plug disk command will fail, this
does not apply to disks with IDE interfaces which can only be activated
in a VM with a Down status

Change-Id: Idd625adb50ceaee3754f317d5751b78e29f7ea25
Bug-Url: https://bugzilla.redhat.com/1055224
Signed-off-by: Tal Nisan <tnisan@redhat.com>