[coverity] Fix 1566353 Resource leak

In the `test-runtime` conformance test suite, ensure that the
`ur_loader_config_handle_t` is always cleaned up even in the event of
assert failures in `SetUp()` by releasing it in `TearDown()`.

Author: kbenzie

test/conformance/runtime/fixtures.h

@@ -11,18 +11,21 @@ struct urTest : ::testing::Test {
 
     void SetUp() override {
         ur_device_init_flags_t device_flags = 0;
-        ur_loader_config_handle_t config;
-        ASSERT_SUCCESS(urLoaderConfigCreate(&config));
-        ASSERT_SUCCESS(
-            urLoaderConfigEnableLayer(config, "UR_LAYER_FULL_VALIDATION"));
-        ASSERT_SUCCESS(urInit(device_flags, config));
-        ASSERT_SUCCESS(urLoaderConfigRelease(config));
+        ASSERT_SUCCESS(urLoaderConfigCreate(&loader_config));
+        ASSERT_SUCCESS(urLoaderConfigEnableLayer(loader_config,
+                                                 "UR_LAYER_FULL_VALIDATION"));
+        ASSERT_SUCCESS(urInit(device_flags, loader_config));
     }
 
     void TearDown() override {
+        if (loader_config) {
+            ASSERT_SUCCESS(urLoaderConfigRelease(loader_config));
+        }
         ur_tear_down_params_t tear_down_params{};
         ASSERT_SUCCESS(urTearDown(&tear_down_params));
     }
+
+    ur_loader_config_handle_t loader_config = nullptr;
 };
 
 struct urAdapterTest : urTest {