Rename shell namespace to service_manager

mash/screenlock/main.cc

Index: mash/screenlock/main.cc
diff --git a/mash/screenlock/main.cc b/mash/screenlock/main.cc
index 5c38955d417033fa666e833948aa234c58168db5..2e5392a492841809e9ea57262e0827cf0a84ad54 100644
--- a/mash/screenlock/main.cc
+++ b/mash/screenlock/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::screenlock::Screenlock);
+  service_manager::ServiceRunner runner(new mash::screenlock::Screenlock);
   return runner.Run(service_request_handle);
 }