SERVER-27244 Status usage compile-time facilities.

There are numerous places in the codebase where `mongo::Status` or
`mongo::StatusWith< T >` objects are returned and never checked.
Many of these are innocuous, but many of them are potentially
severe bugs.  This change introduces facilities to permit
compile-time warning of unchecked `Status` and `StatusWith` usage
on clang compilers.  It introduces an `ignore` function which is
useful to state that a specific "ignored status" case was
intentional.  It not presently an error, in clang builds, to
forget to check a `Status` -- this will come in a later commit.

This also introduces a `transitional_ignore` function, which allows
for easy continual auditing of the codebase for current "whitelisted"
unchecked-status instances.  All present "ignored status" cases
have been marked `transitional_ignore`.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/mongo/db/s/metadata_manager_test.cpp b/src/mongo/db/s/metadata_manager_test.cpp
index 5ba653ac731..a17eed1c6b4 100644
--- a/src/mongo/db/s/metadata_manager_test.cpp
+++ b/src/mongo/db/s/metadata_manager_test.cpp
@@ -81,7 +81,8 @@ protected:
     void setUp() override {
         ShardingMongodTestFixture::setUp();
         serverGlobalParams.clusterRole = ClusterRole::ShardServer;
-        initializeGlobalShardingStateForMongodForTest(ConnectionString(dummyHost));
+        initializeGlobalShardingStateForMongodForTest(ConnectionString(dummyHost))
+            .transitional_ignore();
 
         configTargeter()->setFindHostReturnValue(dummyHost);
     }