[Spark QA] Link to console output on test time out

When tests time out we should link to the Jenkins console output for easy review. We already do this for when tests start or complete normally.

Here's [a recent example](https://github.com/apache/spark/pull/2109#issuecomment-53374032) of where this would be helpful.

Author: nchammas <nicholas.chammas@gmail.com>

Closes #2140 from nchammas/patch-1 and squashes the following commits:

3b26c8d [nchammas] [Spark QA] Link to console output on test time out

dev/run-tests-jenkins

@@ -138,7 +138,7 @@ function post_message () {
   test_result="$?"
 
   if [ "$test_result" -eq "124" ]; then
-    fail_message="**Tests timed out** after a configured wait of \`${TESTS_TIMEOUT}\`."
+    fail_message="**[Tests timed out](${BUILD_URL}consoleFull)** after a configured wait of \`${TESTS_TIMEOUT}\`."
     post_message "$fail_message"
     exit $test_result
   else