Temporarily disabled VerifySlaveLaunchExecutorHook test.

Hook test is flaky and has been temporarily disabled until we have
fixed the synchronization between executorTerminated hook and test
body.

src/tests/hook_tests.cpp

@@ -186,7 +186,7 @@ TEST_F(HookTest, VerifyMasterLaunchTaskHook)
 // Test executor environment decorator hook and remove executor hook
 // for slave.  We expect the environment-decorator hook to create a
 // temporary file and the remove-executor hook to delete that file.
-TEST_F(HookTest, VerifySlaveLaunchExecutorHook)
+TEST_F(HookTest, DISABLED_VerifySlaveLaunchExecutorHook)
 {
   master::Flags masterFlags = CreateMasterFlags();