TSI: free the fixture in destruct() instead of in tsi_test_fixture_destroy() (#28312)

test/core/tsi/fake_transport_security_test.cc

@@ -64,7 +64,7 @@ static void fake_test_check_handshaker_peers(tsi_test_fixture* fixture) {
   validate_handshaker_peers(fixture->server_result);
 }
 
-static void fake_test_destruct(tsi_test_fixture* /*fixture*/) {}
+static void fake_test_destruct(tsi_test_fixture* fixture) { gpr_free(fixture); }
 
 static const struct tsi_test_fixture_vtable vtable = {
     fake_test_setup_handshakers, fake_test_check_handshaker_peers,

test/core/tsi/ssl_transport_security_test.cc

@@ -415,6 +415,7 @@ static void ssl_test_destruct(tsi_test_fixture* fixture) {
       ssl_fixture->server_handshaker_factory);
   tsi_ssl_client_handshaker_factory_unref(
       ssl_fixture->client_handshaker_factory);
+  gpr_free(ssl_fixture);
 }
 
 static const struct tsi_test_fixture_vtable vtable = {

test/core/tsi/transport_security_test_lib.cc

@@ -628,10 +628,9 @@ void tsi_test_fixture_destroy(tsi_test_fixture* fixture) {
   tsi_test_channel_destroy(fixture->channel);
   GPR_ASSERT(fixture->vtable != nullptr);
   GPR_ASSERT(fixture->vtable->destruct != nullptr);
-  fixture->vtable->destruct(fixture);
   gpr_mu_destroy(&fixture->mu);
   gpr_cv_destroy(&fixture->cv);
-  gpr_free(fixture);
+  fixture->vtable->destruct(fixture);
 }
 
 tsi_test_frame_protector_fixture* tsi_test_frame_protector_fixture_create() {