tests: fix flakiness in MctpUtil tests

- Replaced static sleep(3) in SetUp with dynamic system() wait loop for mock mctpd to claim name.
- Added 100ms delay after setupMctpEndpointListener to allow D-Bus match rules to register before triggering events.
- This resolves flakiness in MctpReactorDevice removal and destruction notification tests.

Google-Bug-Id: 509971428
TAG=agy
CONV=20b74d17-8c22-4637-865e-fef8e20edda2

Change-Id: I56b3c191277774ee75ade8a65bc97873938de5b9

tests/test_MctpUtil.cpp

diff --git a/tests/test_MctpUtil.cpp b/tests/test_MctpUtil.cpp
index cf2bfe3..0854d5f 100644
--- a/tests/test_MctpUtil.cpp
+++ b/tests/test_MctpUtil.cpp
@@ -93,8 +93,36 @@
             // clang-format on
             exit(1);
         }
-        // Give mock some time to start and claim names!
-        sleep(3); // NOLINT
+        // Wait for mock to claim names
+        bool ready = false;
+        for (int i = 0; i < 50; i++)
+        {
+            std::string cmd =
+                "busctl call org.freedesktop.DBus /org/freedesktop/DBus "
+                "org.freedesktop.DBus GetNameOwner s "
+                "au.com.codeconstruct.MCTP1 > /dev/null 2>&1";
+            const char* dbusAddr = std::getenv("DBUS_SESSION_BUS_ADDRESS");
+            if (dbusAddr != nullptr)
+            {
+                size_t pos = cmd.find("busctl ");
+                if (pos != std::string::npos)
+                {
+                    cmd.replace(pos, 7,
+                                "busctl --address=" + std::string(dbusAddr) +
+                                    " ");
+                }
+            }
+            int rc = system(cmd.c_str()); // NOLINT(cert-env33-c)
+            if (rc != -1 && WIFEXITED(rc) && WEXITSTATUS(rc) == 0)
+            {
+                ready = true;
+                break;
+            }
+            usleep(100000); // 100ms
+        }
+
+        ASSERT_TRUE(ready)
+            << "Mock mctpd service au.com.codeconstruct.MCTP1 not ready!";
     }
 
     void TearDown() override
@@ -1150,6 +1178,7 @@
         "/xyz/openbmc_project/inventory/system/board/MockBoard/mctp_device";
 
     setupMctpEndpointListener(conn, MctpMessageType::NVME_MI);
+    usleep(100000); // 100ms for match rules to register
 
     // Trigger Add event FIRST!
     std::string addCmd =
@@ -1276,6 +1305,7 @@
         "/xyz/openbmc_project/inventory/system/board/MockBoard/mctp_device";
 
     setupMctpEndpointListener(conn, MctpMessageType::NVME_MI);
+    usleep(100000); // 100ms for match rules to register
 
     // Trigger Add event FIRST!
     std::string addCmd =