Multiple UI fixes and improvements (#4572)

Reverting switch teams code

Fixing change css function

webapp/components/new_channel_modal.jsx

@@ -206,6 +206,7 @@ class NewChannelModal extends React.Component {
         return (
             <span>
                 <Modal
+                    dialogClassName='new-channel__modal'
                     show={this.props.show}
                     bsSize='large'
                     onHide={this.props.onModalDismissed}

webapp/components/sidebar_right_menu.jsx

@@ -68,6 +68,7 @@ export default class SidebarRightMenu extends React.Component {
     getFlagged(e) {
         e.preventDefault();
         getFlaggedPosts();
+        this.hideSidebars();
     }
 
     componentDidMount() {