Address review feedback on hostgroups unit tests (PR #5506)

- test_init.h: remove duplicate test_cleanup_query_processor()
  declaration (copy-paste artifact at line 130)
- test_init.cpp: check MyHGM and PgHGM independently instead of
  using OR guard, so one can't be left null while the other exists

test/tap/test_helpers/test_init.cpp

@@ -173,24 +173,24 @@ void test_cleanup_query_processor() {
 // ============================================================================
 
 int test_init_hostgroups() {
-	if (MyHGM != nullptr || PgHGM != nullptr) {
-		return 0;
-	}
-
 	// HostGroups Manager constructors register Prometheus metrics.
 	if (GloVars.prometheus_registry == nullptr) {
 		GloVars.prometheus_registry = std::make_shared<prometheus::Registry>();
 	}
 
-	MyHGM = new MySQL_HostGroups_Manager();
-	// NOTE: We intentionally do NOT call MyHGM->init() here.
-	// init() starts background threads (HGCU_thread, GTID_syncer)
-	// that run forever and would cause the test process to hang on
-	// exit. The constructor alone sets up the internal SQLite3
-	// database and all data structures needed for unit testing.
+	if (MyHGM == nullptr) {
+		MyHGM = new MySQL_HostGroups_Manager();
+		// NOTE: We intentionally do NOT call MyHGM->init() here.
+		// init() starts background threads (HGCU_thread, GTID_syncer)
+		// that run forever and would cause the test process to hang on
+		// exit. The constructor alone sets up the internal SQLite3
+		// database and all data structures needed for unit testing.
+	}
 
-	PgHGM = new PgSQL_HostGroups_Manager();
-	// PgHGM->init() is a no-op, but we skip it for consistency.
+	if (PgHGM == nullptr) {
+		PgHGM = new PgSQL_HostGroups_Manager();
+		// PgHGM->init() is a no-op, but we skip it for consistency.
+	}
 
 	return 0;
 }

test/tap/test_helpers/test_init.h

@@ -127,6 +127,5 @@ int test_init_hostgroups();
  * Destroys MyHGM and PgHGM, setting them back to nullptr.
  */
 void test_cleanup_hostgroups();
-void test_cleanup_query_processor();
 
 #endif /* TEST_INIT_H */