Fix issue when local properties pass from parent to child thread
Fix issue with spark_ec2 seeing empty security groups

Under unknown, but occasional, circumstances, reservation.groups is empty
despite reservation.instances each having groups. This means that the
spark_ec2 get_existing_clusters() method would fail to find any instances.
To fix it, we simply use the instances' groups as the source of truth.

Note that this is actually just a revival of PR #827, now that the issue
has been reproduced.
Merge pull request #938 from ilikerps/master

Fix issue with spark_ec2 seeing empty security groups
After unit tests, clear port properties unconditionally

In MapOutputTrackerSuite, the "remote fetch" test sets spark.driver.port
and spark.hostPort, assuming that they will be cleared by
LocalSparkContext. However, the test never sets sc, so it remains null,
causing LocalSparkContext to skip clearing these properties. Subsequent
tests therefore fail with java.net.BindException: "Address already in
use".

This commit makes LocalSparkContext clear the properties even if sc is
null.
Add "org.apache." prefix to packages in spark-class

Lacking this, the if/case statements never trigger on Spark 0.8.0+.
Add barrier for local properties unit test and fix some styles
Merge pull request #940 from ankurdave/clear-port-properties-after-tests

After unit tests, clear port properties unconditionally
Merge pull request #941 from ilikerps/master

Add "org.apache." prefix to packages in spark-class
Merge pull request #937 from jerryshao/localProperties-fix

Fix PR926 local properties issues in Spark Streaming like scenarios
Refactor FairSchedulableBuilder:
1. Configuration can be read from classpath if not set explicitly.
2. Add missing close handler.
Remove infix style and others
Change Exception to NoSuchElementException and minor style fix
Merge pull request #928 from jerryshao/fairscheduler-refactor

Refactor FairSchedulableBuilder