fix aws missing init

pkg/compute/hostdrivers/aws.go

@@ -12,6 +12,11 @@ type SAwsHostDriver struct {
 	SManagedVirtualizationHostDriver
 }
 
+func init() {
+	driver := SAwsHostDriver{}
+	models.RegisterHostDriver(&driver)
+}
+
 func (self *SAwsHostDriver) GetHostType() string {
 	return models.HOST_TYPE_AWS
 }