ShardServerCatalogCacheLoader shouldn't replace error codes with OperationFailed

The ShardServerCatalogCache loader currently replaces the error code of not ok statuses returned from several reads performed as part of a metadata refresh with OperationFailed - here, here, and here. This can prevent our test infrastructure from automatically retrying if the original error codes were retryable. Instead, the loader should preserve the original error codes, possibly by using uassertStatusOKWithContext() (e.g. here).