Remove use of system properties in FileServerSuite
Remove TestUtils.setSystemProperty, since it is subsumed by the ResetSystemProperties trait.
Remove use of system properties in SparkContextSuite
Remove System.setProperty calls in DistributedSuite
Remove setProperty calls in JobCancellationSuite
Remove setProperty calls in SparkContextSchedulerCreationSuite
Remove setProperty call in TaskSchedulerImplSuite
Fix trait ordering
Remove setProperty call in TaskResultGetterSuite.
Clarify ResetSystemProperties trait inheritance ordering.
Add note on why SparkSubmitSuite needs ResetSystemProperties
Remove setProperty use in LocalJavaStreamingContext
Replace setProperty uses in two example programs / tools