test: initialize creation_status (#37538)

Commit Message: test: initialize creation_status
Additional Description:
Initialize a value to clarify initial value.

Risk Level: low - tests only
Testing: N/A
Docs Changes: N/A
Release Notes: N/A
Platform Specific Features: N/A

Signed-off-by: Adi Suissa-Peleg <adip@google.com>

test/common/upstream/cluster_manager_impl_test.cc

@@ -316,7 +316,7 @@ class ClusterManagerImplTest : public testing::Test {
     yaml += enable_merge_window ? merge_window_enabled : merge_window_disabled;
 
     const auto& bootstrap = parseBootstrapFromV3Yaml(yaml);
-    absl::Status creation_status;
+    absl::Status creation_status = absl::OkStatus();
     cluster_manager_ = std::make_unique<MockedUpdatedClusterManagerImpl>(
         bootstrap, factory_, factory_.server_context_, factory_.stats_, factory_.tls_,
         factory_.runtime_, factory_.local_info_, log_manager_, factory_.dispatcher_, admin_,