Use 'publish' post_status when querying posts for Stats endpoint.

Previously, the post_status logic was: if the default "draft" post
status is something other than "draft", use that. Otherwise, use
"publish". This must be an error, since it implies that using a non-
default draft status means that you only want to count drafts in
your stats. Instead, we always want to count published posts only.

See #933.

Controllers/Stats.php

@@ -198,13 +198,7 @@ private function meta_query_args() {
 	 * @return string
 	 */
 	private function post_status_query_args() {
-		$status = get_option( PF_SLUG . '_draft_post_status', 'draft' );
-		if ( 'draft' !== $status ) {
-			$status_check = $status;
-		} else {
-			$status_check = 'publish';
-		}
-		return $status_check;
+		return 'publish';
 	}
 
 	/**