[SPARK-7287] [SPARK-8567] [TEST] Add sc.stop to applications in SparkSubmitSuite

Hopefully, this suite will not be flaky anymore.

Author: Yin Huai <yhuai@databricks.com>

Closes #7027 from yhuai/SPARK-8567 and squashes the following commits:

c0167e2 [Yin Huai] Add sc.stop().

core/src/test/scala/org/apache/spark/deploy/SparkSubmitSuite.scala

@@ -548,6 +548,7 @@ object JarCreationTest extends Logging {
     if (result.nonEmpty) {
       throw new Exception("Could not load user class from jar:\n" + result(0))
     }
+    sc.stop()
   }
 }
 
@@ -573,6 +574,7 @@ object SimpleApplicationTest {
           s"Master had $config=$masterValue but executor had $config=$executorValue")
       }
     }
+    sc.stop()
   }
 }
 

sql/hive/src/test/resources/regression-test-SPARK-8489/Main.scala

@@ -38,6 +38,7 @@ object Main {
     val df = hc.createDataFrame(Seq(MyCoolClass("1", "2", "3")))
     df.collect()
     println("Regression test for SPARK-8489 success!")
+    sc.stop()
   }
 }