Fixes for destruction

src/core/lib/iomgr/tcp_posix.c

@@ -131,6 +131,7 @@ static void tcp_free(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
   grpc_fd_orphan(exec_ctx, tcp->em_fd, tcp->release_fd_cb, tcp->release_fd,
                  "tcp_unref_orphan");
   gpr_slice_buffer_destroy(&tcp->last_read_buffer);
+  grpc_buffer_user_destroy(exec_ctx, &tcp->buffer_user);
   gpr_free(tcp->peer_string);
   gpr_free(tcp);
 }

test/core/util/mock_endpoint.c

@@ -90,6 +90,7 @@ static void me_really_destroy(grpc_exec_ctx *exec_ctx, void *mp,
                               grpc_error *error) {
   grpc_mock_endpoint *m = mp;
   gpr_slice_buffer_destroy(&m->read_buffer);
+  grpc_buffer_user_destroy(exec_ctx, &m->buffer_user);
   gpr_free(m);
 }