Editor: Reset Post Edits when switching posts in the post editor

If we create a new post, switch to a draft from the sidebar without saving
and coming back to /post/new again, some initial post edits were kept instead of having a fresh new post

client/post-editor/post-editor.jsx

@@ -156,6 +156,12 @@ export const PostEditor = React.createClass( {
 
 	componentWillReceiveProps: function( nextProps ) {
 		const { siteId, postId } = this.props;
+
+		// When switching posts, reset post edits for the post we're leaving
+		if ( nextProps.postId !== postId ) {
+			this.props.resetPostEdits( siteId, postId );
+		}
+
 		if ( nextProps.siteId === siteId && nextProps.postId !== postId ) {
 			// make sure the history entry has the post ID in it, but don't dispatch
 			page.replace( nextProps.editPath, null, false, false );