Writes adb_mode to config file

Removed (accidentally I think) by ag/4494283

Test: local run
Change-Id: I96138f6b95f99b10c27baeeb424cce8f833a59f6
diff --git a/host/commands/launch/main.cc b/host/commands/launch/main.cc
index 1a077f8..816e8b1 100644
--- a/host/commands/launch/main.cc
+++ b/host/commands/launch/main.cc
@@ -504,6 +504,7 @@
   config->set_y_res(FLAGS_y_res);
   config->set_refresh_rate_hz(FLAGS_refresh_rate_hz);
   config->set_gdb_flag(FLAGS_qemu_gdb);
+  config->set_adb_mode(FLAGS_adb_mode);
   if (FLAGS_kernel_path.size()) {
     config->set_kernel_image_path(FLAGS_kernel_path);
   } else {