Increase robustness when reading PEX-INFO

Bugs closed: AURORA-456

Reviewed at https://reviews.apache.org/r/27586/
Convert most uses of Mock to create_autospec, remove some uses of mocking altogether.

Bugs closed: AURORA-889

Reviewed at https://reviews.apache.org/r/27628/
Remove duplicate call to log handling code. This duplicate call added another
stderr handler to the logger which caused each message to be printed twice to
stderr.

Bugs closed: AURORA-793

Reviewed at https://reviews.apache.org/r/27650/
Mark inotify disk collector test as flaky.

Bugs closed: AURORA-916

Reviewed at https://reviews.apache.org/r/27630/
Replace twitter.commons.io.FileUtils dependency w/ guava's Files

Reviewed at https://reviews.apache.org/r/27545/
Remove SchedulerActive, replace with explicit services.

This is the first part of a larger change that will allow us to
make pubsub events async as it makes the dependency on subscribers
processing a SchedulerActive event explicit.

Testing Done:
./gradlew -Pq build
test_end_to_end.sh

Bugs closed: AURORA-920

Reviewed at https://reviews.apache.org/r/27716/
Fixing the log replay for the job update history pruner.

Bugs closed: AURORA-912

Reviewed at https://reviews.apache.org/r/27598/
Fixing beta-update OK status messaging.

Bugs closed: AURORA-784

Reviewed at https://reviews.apache.org/r/27712/
Simplify management of the driver lifecycle using AbstractidleService.

Bugs closed: AURORA-920

Reviewed at https://reviews.apache.org/r/27746/
Use async eventbus

This change uses AsyncEventBus in production code. Some test code
still expects eventSink.post() to block. I plan to address in a
follow-up review.

Testing Done:
./gradlew -Pq build

Bugs closed: AURORA-920

Reviewed at https://reviews.apache.org/r/27762/
Undo 0.6.0 .auroraversion and CHANGELOG changes to prepare for 0.6.0-RC1

Bugs closed: AURORA-711

Reviewed at https://reviews.apache.org/r/27830/
Updating CHANGELOG for 0.6.0 release.
Incrementing snapshot version to 0.6.1-SNAPSHOT.
Print out the job url after scheduling a cron job.

Bugs closed: AURORA-857

Reviewed at https://reviews.apache.org/r/27657/
Remove stracktrace redirection.

Bugs closed: AURORA-896

Reviewed at https://reviews.apache.org/r/27710/
Add test coverage for WriteAheadStorage.

Reviewed at https://reviews.apache.org/r/27542/
Create the PyCharm project configuration for easier IDE setup.

Reviewed at https://reviews.apache.org/r/27779/
Fix false passing test case in SchedulerDriverServiceTest.

Reviewed at https://reviews.apache.org/r/27772/
Make it easier to request another ReviewBot run, and flag diffs that seem to lack test coverage.

Reviewed at https://reviews.apache.org/r/27770/
Fix missing paren in review bot.

Reviewed at https://reviews.apache.org/r/27880/