Mark service/isolate_lifecycle_test flaky on all platforms.

runtime/observatory/tests/service/service.status

Index: runtime/observatory/tests/service/service.status
diff --git a/runtime/observatory/tests/service/service.status b/runtime/observatory/tests/service/service.status
index 9a41163969718d154ccbbb231d914a5b4f499e41..b891f4f8a7ae37eb8599451c8da4f86bcc741aea 100644
--- a/runtime/observatory/tests/service/service.status
+++ b/runtime/observatory/tests/service/service.status
@@ -8,6 +8,7 @@ reload_sources_test: Pass, Slow # Reload is slow on the bots
 get_retained_size_rpc_test: Pass, RuntimeError # Issue 28193
 pause_on_start_and_exit_test: Pass, RuntimeError # Issue 28624
 pause_on_start_then_step_test: Pass, RuntimeError # Issue 28624
+isolate_lifecycle_test: Pass, RuntimeError # Issue 24174
 
 [$runtime == vm && $compiler == none && $system == fuchsia]
 *: Skip  # Not yet triaged.
@@ -15,7 +16,6 @@ pause_on_start_then_step_test: Pass, RuntimeError # Issue 28624
 [ ($compiler == none || $compiler == precompiler) && ($runtime == vm || $runtime == dart_precompiled) ]
 evaluate_activation_test/instance: RuntimeError # http://dartbug.com/20047
 evaluate_activation_test/scope: RuntimeError # http://dartbug.com/20047
-isolate_lifecycle_test: Pass, RuntimeError # Issue 24174
 
 # Debugger location tests are slow in debug mode.
 [ $mode == debug ]