Comment 2 for bug 1883220

Hi tosca-parser teams!
I'm working with tacker project.

Original bug ticket is https://bugs.launchpad.net/tacker/+bug/1881219.
This problem seems to occur by tosca-parser's bug.

It seems to work fine if I remove `not nodetemplate.sub_mapping_tosca_template` from the if expression in method `_is_sub_mapped_node`.

So I will push a patch fix as above, and could you check this details and patch contents.
Thanks!