Maintain exec_ctx flags initialization as it was before

src/core/lib/iomgr/executor.cc

@@ -145,7 +145,7 @@ static void executor_thread(void* arg) {
   thread_state* ts = (thread_state*)arg;
   gpr_tls_set(&g_this_thread_state, (intptr_t)ts);
 
-  grpc_core::ExecCtx _local_exec_ctx;
+  grpc_core::ExecCtx _local_exec_ctx(0);
 
   size_t subtract_depth = 0;
   for (;;) {

src/core/lib/iomgr/timer_manager.cc

@@ -273,7 +273,7 @@ static void timer_thread_cleanup(completed_thread* ct) {
 static void timer_thread(void* completed_thread_ptr) {
   // this threads exec_ctx: we try to run things through to completion here
   // since it's easy to spin up new threads
-  grpc_core::ExecCtx _local_exec_ctx;
+  grpc_core::ExecCtx _local_exec_ctx(0);
   timer_main_loop();
 
   timer_thread_cleanup((completed_thread*)completed_thread_ptr);

src/core/lib/surface/init.cc

@@ -175,7 +175,7 @@ void grpc_init(void) {
 void grpc_shutdown(void) {
   int i;
   GRPC_API_TRACE("grpc_shutdown(void)", 0, ());
-  grpc_core::ExecCtx _local_exec_ctx;
+  grpc_core::ExecCtx _local_exec_ctx(0);
   gpr_mu_lock(&g_init_mu);
   if (--g_initializations == 0) {
     grpc_executor_shutdown();