add better OS detection for BDM

ec2_vol

@@ -150,11 +150,15 @@ def main():
     # In future this needs to be more dynamic but combining block device mapping best practices
     # (bounds for devices, as above) with instance.block_device_mapping data would be tricky. For me ;)
 
+    # Use password data attribute to tell whether the instance is Windows or Linux
     if device_name is None and instance:
         try:
-            if inst.root_device_type != 'ebs':
+            if inst.get_password_data == '':
                 device_name = '/dev/sdf'
                 attach = volume.attach(inst.id, device_name)
+                while volume.attachment_state() != 'attached':
+                    time.sleep(3)
+                    volume.update()
             else:
                 device_name = '/dev/sdb'
                 attach = volume.attach(inst.id, device_name)