The `oif_ps` attr expects a list of dicts but it also supports keyword 'default'.
When the playbook specifies `oif_ps: default` the `nxos_igmp_interface` module fails:
```
"msg": "Elements value for option oif_ps is of type <type 'str'> and we were unable to convert to dict: dictionary requested, could not parse JSON or key=value"
```
This test used to work afaik so I believe `AnsibleModule` may have changed at some point to enforce strict type checking, causing this failure. I did not see another way to handle both list & str types for the same attr so I just set it to `raw`.
`nxos_igmp_interface/tests/common/sanity` now has 100% pass rate.
b678139e68