Rename shell namespace to service_manager

mash/app_driver/main.cc

Index: mash/app_driver/main.cc
diff --git a/mash/app_driver/main.cc b/mash/app_driver/main.cc
index 8d1d09d919c2ed0c923a458ddf28eee0179cd0da..7645d4cbc69fb38d1048215bd8ae4abc806ddfc6 100644
--- a/mash/app_driver/main.cc
+++ b/mash/app_driver/main.cc
@@ -7,6 +7,6 @@
 #include "services/service_manager/public/cpp/service_runner.h"
 
 MojoResult ServiceMain(MojoHandle service_request_handle) {
-  shell::ServiceRunner runner(new mash::app_driver::AppDriver);
+  service_manager::ServiceRunner runner(new mash::app_driver::AppDriver);
   return runner.Run(service_request_handle);
 }