Terminate executors that aren't needed.

If we launch an executor and then kill the task immediately after, make
sure we also terminate the executor when there are no other tasks.

Review: https://reviews.apache.org/r/11125
Make sure you clean up the cgroups test.

Sometimes the cgroup test fails because the directory is already there.
This should ensure that it gets cleanup up in that case before we exit.

We'll also check that it exists before we try creating it.  If it
already exists, we'll skip the creation.

Review: https://reviews.apache.org/r/11126
More cgroup killTask() logging.

Review: https://reviews.apache.org/r/11129
Increase JVM memory overhead.

Review: https://reviews.apache.org/r/11130
For cgroups killTasks(): kill, freeze, kill, thaw.

Review: https://reviews.apache.org/r/11131
Don't accept offers on the same host/port.

We'll try to find a port combination that hasn't already been used to
launch a TaskTracker.

Review: https://reviews.apache.org/r/11161/
Write Mesos JobTracker stats to state file.

Review: https://reviews.apache.org/r/11165/
Pretty-print resource type with parsing error.

Review: https://reviews.apache.org/r/11486
Strip spaces and quotes --resources arg.

Review: https://reviews.apache.org/r/11487
Use string comparison for TaskID.

Review: https://reviews.apache.org/r/11488
s/hadoopJobs/jobs/g in Hadoop scheduler.

Review: https://reviews.apache.org/r/11489
Refactor Hadoop job completion.

Review: https://reviews.apache.org/r/11603
Stop tracker timer when we terminate tasks.

Review: https://reviews.apache.org/r/11604
Add --enable-debug configure flag.

Review: https://reviews.apache.org/r/11605
Increase slave timeout.

Review: https://reviews.apache.org/r/11606
Use XZ (LZMA) for package on Linuxes.

Review: https://reviews.apache.org/r/11112
Log executor output to syslog.

Review: https://reviews.apache.org/r/11123
Turn down noise from ZooKeeper.

Review: https://reviews.apache.org/r/11127
Fix hadoop 0.20.205.0 dist.

Review: https://reviews.apache.org/r/11662