Avoid passing global state into websocket_actions.jsx in webapp

This ticket is regarding the way we handle state actions in webapp. Similar to the util functions, we are passing the state and dispatch directly from our imported global store in the action creators.

In order to make the action creators more predictable and improve their testability we need to refactor the way we handle action creators and make sure they are always passed to mapDispatchToProps in the connected components.

Files: websocket_actions.jsx

Proposed change in post_actions.jsx:

const addPostToSearchResults = (postId) => (dispatch, getState) => {
// get the state from getState
  ......
  dispatch({
            type: SearchTypes.RECEIVED*SEARCH*POSTS,
            data: {posts, order: newResults},
        });
} 

and then we call it dispatch(addPostToSearchResults(postId));

NOTE: Calling getState is fine as long as it's coming from thunk inside the component. We don't want to import it from stores/redux_store

---

If you're interested please comment here and come join our "Contributors" community channel on our daily build server, where you can discuss questions with community members and the Mattermost core team. For technical advice or questions, please join our "Developers" community channel.

New contributors please see our Developer's Guide.

JIRA: https://mattermost.atlassian.net/browse/MM-47360