Customizer: Prevent preview from loading during QUnit tests and causing an XHR cross-domain error.

Fixes #32666.


git-svn-id: https://develop.svn.wordpress.org/trunk@33120 602fd350-edb4-49c9-b593-d223f7449a82

tests/qunit/fixtures/customize-settings.js

@@ -133,3 +133,11 @@ window._wpCustomizeSettings = {
 	}
 };
 window._wpCustomizeControlsL10n = {};
+
+jQuery.ajaxSetup( {
+	beforeSend: function( e, data ) {
+		if ( data.data.indexOf( 'wp_customize' ) !== -1 ) {
+			return false;
+		}
+	}
+} );