fixed typo in test name

[SVN r29311]

status/explicit-failures-markup.xml

@@ -906,7 +906,7 @@
         </mark-expected-failures>
         <mark-expected-failures>
             <test name="bzip2_test"/>
-            <test name="file_descriptor"/>
+            <test name="file_descriptor_test"/>
             <test name="mapped_file_test"/>
             <toolset name="*como-4_3_3*"/>
             <note author="Jonathan Turkanis">