Move destroy to finally block

Per comment in #4320.

Author: Andrew Or

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

@@ -499,12 +499,15 @@ class SparkSubmitSuite
       Seq("./bin/spark-submit") ++ args,
       new File(sparkHome),
       Map("SPARK_TESTING" -> "1", "SPARK_HOME" -> sparkHome))
-    val exitCode = failAfter(60 seconds) { process.waitFor() }
-    // Ensure we still kill the process in case it timed out
-    process.destroy()
-    // If the process did not return cleanly, fail the test
-    if (exitCode != 0) {
-      fail(s"Process returned with exit code $exitCode. See the log4j logs for more detail.")
+
+    try {
+      val exitCode = failAfter(60 seconds) { process.waitFor() }
+      if (exitCode != 0) {
+        fail(s"Process returned with exit code $exitCode. See the log4j logs for more detail.")
+      }
+    } finally {
+      // Ensure we still kill the process in case it timed out
+      process.destroy()
     }
   }