Introduce machinery to allow tests to register plugins
diff --git a/test/core/end2end/fixtures/h2_full+trace.c b/test/core/end2end/fixtures/h2_full+trace.c
index 986a06b..7599412 100644
--- a/test/core/end2end/fixtures/h2_full+trace.c
+++ b/test/core/end2end/fixtures/h2_full+trace.c
@@ -116,6 +116,7 @@
 #endif
 
   grpc_test_init(argc, argv);
+  grpc_end2end_tests_pre_init();
   grpc_init();
 
   GPR_ASSERT(0 == grpc_tracer_set_enabled("also-doesnt-exist", 0));