Make RS Build Work on impala-ec2 label

Infra has teh impala-ec2 label that was designed for the impala builds on ec2. These machines can be fired up on demand to help ease jenkins backlog. Our RS builds currently don't work on these labels. I don't have any hard proof that they ever did but it's likely that they did at one time. It would be helpful to the team productivity if we make these work again.

Latest error from this build: http://sandbox.jenkins.cloudera.com/job/record-service-gerrit-client/696/

11:48:26 +++ cd /data/jenkins/workspace/record-service-gerrit-client/repos/Impala/tests
11:48:26 +++ ./run-tests.py query_test/test_hive_serde.py
11:48:26 Traceback (most recent call last):
11:48:26 File "./run-tests.py", line 86, in <module>
11:48:26 test_executor.run_tests(args)
11:48:26 File "./run-tests.py", line 55, in run_tests
11:48:26 exit_code = pytest.main(args)
11:48:26 File "/usr/lib/python2.6/site-packages/_pytest/config.py", line 48, in main
11:48:26 config.pluginmanager.check_pending()
11:48:26 File "/usr/lib/python2.6/site-packages/_pytest/vendored_packages/pluggy.py", line 490, in check_pending
11:48:26 (name, hookimpl.plugin))
11:48:26 _pytest.vendored_packages.pluggy.PluginValidationError: unknown hook 'pytest_xdist_setupnodes' in plugin <module 'tests.conftest' from '/data/jenkins/workspace/record-service-gerrit-client/repos/Impala/tests/conftest.py'>
11:48:36 Process leaked file descriptors. See http://wiki.jenkins-ci.org/display/JENKINS/Spawning+processes+from+build for more information
11:48:36 Build step 'Execute shell' marked build as failure
11:48:36 Archiving artifacts
11:48:36 Recording test results
11:48:37 Publish JUnit test result report is waiting for a checkpoint on record-service-gerrit-client #694
12:32:42 ERROR: Publisher hudson.tasks.junit.JUnitResultArchiver aborted due to exception
12:32:42 java.lang.InterruptedException
12:32:42 at java.lang.Object.wait(Native Method)
12:32:42 at java.lang.Object.wait(Object.java:503)
12:32:42 at hudson.model.Run$RunExecution$CheckpointSet.waitForCheckPoint(Run.java:1525)
12:32:42 at hudson.model.Run.waitForCheckpoint(Run.java:1479)
12:32:42 at hudson.model.CheckPoint.block(CheckPoint.java:156)
12:32:42 at hudson.tasks.junit.JUnitResultArchiver.perform(JUnitResultArchiver.java:160)
12:32:42 at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
12:32:42 at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:785)
12:32:42 at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:757)
12:32:42 at hudson.model.Build$BuildExecution.post2(Build.java:183)
12:32:42 at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:706)
12:32:42 at hudson.model.Run.execute(Run.java:1690)
12:32:42 at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
12:32:42 at hudson.model.ResourceController.execute(ResourceController.java:88)
12:32:42 at hudson.model.Executor.run(Executor.java:246)
12:32:42 Finished: FAILURE