Suppressed a findbugs warning to do with System.exit.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.20-security@1131266 13f79535-47bb-0310-9956-ffa450edef68

src/test/findbugsExcludeFile.xml

@@ -126,4 +126,10 @@
        <Class name="org.apache.hadoop.mapred.Child" />
        <Bug pattern="DM_EXIT" />
      </Match>
+
+     <Match>
+       <Class name="org.apache.hadoop.mapreduce.security.token.DelegationTokenRenewal$DelegationTokenCancelThread" />
+       <Method name="run" />
+       <Bug pattern="DM_EXIT" />
+    </Match>
 </FindBugsFilter>