Outdent RTL sub list loose text direction

[garry.yao]

1. Load the editor with the following content and selection:

   <ul>
   	<li>foo
   		<ul style="direction: rtl">
   			<li>bar^</li>
   		</ul>
   	</li>
   </ul>
   

2. Press the "Decrease Indent" button

• Actual Result: RTL list item "bar" now has become LTR

[garry.yao]

Regression of [7535].

[garry.yao]

Updated ​http://ckeditor.t/tt/9057/1.html

Fixed with [7548].