fix SparkContextSchedulerCreationSuite test error

run test with the master branch with this command 
sbt/sbt -Pyarn -Phadoop-2.3 -Dhadoop.version=2.3.0 -Pkinesis-as -Phive-thriftserver "test-only org.apache.spark.SparkContextSchedulerCreationSuite"

get this error:
[info] SparkContextSchedulerCreationSuite:
[info] - bad-master
[info] - local
[info] - local-*
[info] - local-n
[info] - local-*-n-failures
[info] - local-n-failures
[info] - bad-local-n
[info] - bad-local-n-failures
[info] - local-default-parallelism
[info] - simr
[info] - local-cluster
[info] - yarn-cluster
[info] - yarn-standalone
[info] - yarn-client
[info] - mesos fine-grained
[info] - mesos coarse-grained *** FAILED ***
[info]   Spark home is not set; set it through the spark.home system property, the SPARK_HOME environment variable or the SparkContext constructor (SparkContextSchedulerCreationSuite.scala:158)
 
move "val sparkHome..." to   createCommand method fix it.