[SPARK-11134][CORE] Increase LauncherBackendSuite timeout.

This test can take a little while to finish on slow / loaded machines.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #9235 from vanzin/SPARK-11134.

core/src/test/scala/org/apache/spark/launcher/LauncherBackendSuite.scala

@@ -54,13 +54,13 @@ class LauncherBackendSuite extends SparkFunSuite with Matchers {
       .startApplication()
 
     try {
-      eventually(timeout(10 seconds), interval(100 millis)) {
+      eventually(timeout(30 seconds), interval(100 millis)) {
         handle.getAppId() should not be (null)
       }
 
       handle.stop()
 
-      eventually(timeout(10 seconds), interval(100 millis)) {
+      eventually(timeout(30 seconds), interval(100 millis)) {
         handle.getState() should be (SparkAppHandle.State.KILLED)
       }
     } finally {