buffet: Don't assume that ID is not in command_owners_

OnCommandAdded is called before return from CommandManager::AddCommand,
so ID with not user is in container.

BUG=brillo:1226
TEST=FEATURES=test emerge-gizmo buffet

Change-Id: Ib2f5020070b046cb2d94f31f0311843d4309ab9b
Reviewed-on: https://chromium-review.googlesource.com/281812
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>

buffet/privet/cloud_delegate.cc

diff --git a/buffet/privet/cloud_delegate.cc b/buffet/privet/cloud_delegate.cc
index bc23f5e..86c93cc 100644
--- a/buffet/privet/cloud_delegate.cc
+++ b/buffet/privet/cloud_delegate.cc
@@ -182,7 +182,7 @@
     if (!command_manager_->AddCommand(command, role, &id, &error))
       return error_callback.Run(error.get());
 
-    CHECK(command_owners_.emplace(id, user_info.user_id()).second);
+    command_owners_[id] = user_info.user_id();
     success_callback.Run(*command_manager_->FindCommand(id)->ToJson());
   }