* Check that union Jinja filter can be chained
* set filters: fix unexpected templating type error
this error occurs with Jinja 2.10 since 32ec69d827,
for example when union filters are chained:
$ ansible all -i localhost, -mdebug -a"msg={{ []|union([])|union([]) }}"
localhost | FAILED! => {
"msg": "Unexpected templating type error occurred on ({{ []|union([])|union([]) }}):
unsupported operand type(s) for +: 'set' and 'list'"
}
b76c4c840e