feed creation should fully resolve the namespace before calling the provider action

when a trigger is created from a feed, the CLI does not fully resolve the trigger name and instead uses `/_` as in:

```json
{
"authKey":"...",
"lifecycleEvent":"CREATE",
"triggerName":"/_/t"
}
```

The namespace should be resolved - this can be done on the client by looking up the namespace `eg equivalent of wsk namespace list`.

The provider can also resolve the namespace by doing the namespace lookup as well. Today, it seems this is being done in some providers by picking up the activation's `__OW_NAMESPACE` property from the activation context.