[sql-lab] performance updates - make ui more responsive (#2469)

* remove network status feature

* only fetch queries if there are started or running queries

* don't use local storage

* remove last network status from actions

* don't remove support for local storage

* address pr comments and linting

* use .some rather than .forEach

superset/assets/javascripts/SqlLab/components/SqlEditorLeftBar.jsx

@@ -1,6 +1,6 @@
 const $ = window.$ = require('jquery');
 import React from 'react';
-import { Label, Button } from 'react-bootstrap';
+import { Button } from 'react-bootstrap';
 import TableElement from './TableElement';
 import AsyncSelect from '../../components/AsyncSelect';
 import Select from 'react-virtualized-select';
@@ -10,12 +10,10 @@ const propTypes = {
   queryEditor: React.PropTypes.object.isRequired,
   tables: React.PropTypes.array,
   actions: React.PropTypes.object,
-  networkOn: React.PropTypes.bool,
 };
 
 const defaultProps = {
   tables: [],
-  networkOn: true,
   actions: {},
 };
 
@@ -27,7 +25,6 @@ class SqlEditorLeftBar extends React.PureComponent {
       schemaOptions: [],
       tableLoading: false,
       tableOptions: [],
-      networkOn: true,
     };
   }
   componentWillMount() {
@@ -125,17 +122,12 @@ class SqlEditorLeftBar extends React.PureComponent {
     this.refs[ref].hide();
   }
   render() {
-    let networkAlert = null;
-    if (!this.props.networkOn) {
-      networkAlert = <p><Label bsStyle="danger">OFFLINE</Label></p>;
-    }
     const shouldShowReset = window.location.search === '?reset=1';
     const options = this.state.tableOptions;
     const filterOptions = createFilterOptions({ options });
     return (
       <div className="scrollbar-container">
         <div className="clearfix sql-toolbar scrollbar-content">
-          {networkAlert}
           <div>
             <AsyncSelect
               dataEndpoint="/databaseasync/api/read?_flt_0_expose_in_sqllab=1"