Form dialog UI: Support on cancel action

If args.cancel is passed to createForm widget, call it when cancel button is
clicked.

Example:

createForm: {
    cancel: function() { ... },
    ...
}
Session expire: show overlay on dialog to prevent clicking in UI
CLOUDSTACK-6103: Pass VM iso information along with
PrepareForMigrationCommand, so that destination hypervisor can
mount pool. This further exposed an issue for KVM where iso
was not getting cleaned up upon successful migration, fixed as well.
add new devcloud-kvm config
CLOUDSTACK-6112. Adding VPC router to a guest network fails with StringIndexOutOfBoundsException.