fix: fix SpotBugs NP warning and Error Prone @var check

- Always create a fresh HostConfig to avoid null dereference path
- Inline mkdirs() result to avoid non-constant variable

Signed-off-by: Hongxin Liang <honnix@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: honnix

integration-tests/src/test/java/org/flyte/SerializeJavaIT.java

@@ -40,8 +40,7 @@ void testSerializeWorkflows() {
       // with the project root as working directory
       String serializePath = "integration-tests/target/protos";
       File tempDir = new File("../" + serializePath);
-      boolean created = tempDir.mkdirs();
-      if (!created && !tempDir.exists()) {
+      if (!tempDir.mkdirs() && !tempDir.exists()) {
         throw new IOException("Unable to create path");
       }
 

integration-tests/src/test/java/org/flyte/utils/FlyteSandboxContainer.java

@@ -160,18 +160,13 @@ private static void patchInsecureEnvVar() {
     // k3s requires tmpfs mounts and cgroupns=host on Linux (CI)
     withTmpFs(Map.of("/run", "", "/var/run", ""));
     withCreateContainerCmdModifier(
-        cmd -> {
-          HostConfig hostConfig = cmd.getHostConfig();
-          if (hostConfig == null) {
-            hostConfig = new HostConfig();
-            cmd.withHostConfig(hostConfig);
-          }
-          hostConfig
-              .withCgroupnsMode("host")
-              // host.docker.internal is needed by the bootstrap to template manifests;
-              // Docker Desktop adds it automatically, but Linux Docker does not
-              .withExtraHosts("host.docker.internal:host-gateway");
-        });
+        cmd ->
+            cmd.withHostConfig(
+                new HostConfig()
+                    .withCgroupnsMode("host")
+                    // host.docker.internal is needed by the bootstrap to template manifests;
+                    // Docker Desktop adds it automatically, but Linux Docker does not
+                    .withExtraHosts("host.docker.internal:host-gateway")));
 
     withNetworkAliases("flyte");