User Query: Don't blindly re-append new meta queries for capabilities.

fixes #21119.


git-svn-id: https://develop.svn.wordpress.org/trunk@28087 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/user/query.php

@@ -101,6 +101,9 @@ class Tests_User_Query extends WP_UnitTestCase {
 		$this->assertEquals( $names, $values );
 	}
 
+	/**
+	 * @ticket 21119
+	 */
 	function test_prepare_query() {
 		$query = new WP_User_Query();
 		$this->assertEmpty( $query->query_fields );