Don't try to inject main_msg if landfill_msg fails
Don't try to inject main_msg if landfill_msg fails

Per @trink, the failure will discard all messages so even if one
was successful it will never see the light of day.

mreid-moz/data-pipeline,kparlante/data-pipeline,whd/data-pipeline,acmiyaguchi/data-pipeline,mozilla-services/data-pipeline,nathwill/data-pipeline,mreid-moz/data-pipeline,whd/data-pipeline,sapohl/data-pipeline,mreid-moz/data-pipeline,nathwill/data-pipeline,nathwill/data-pipeline,sapohl/data-pipeline,whd/data-pipeline,mozilla-services/data-pipeline,whd/data-pipeline,sapohl/data-pipeline,acmiyaguchi/data-pipeline,mozilla-services/data-pipeline,mozilla-services/data-pipeline,acmiyaguchi/data-pipeline,kparlante/data-pipeline,kparlante/data-pipeline,kparlante/data-pipeline,sapohl/data-pipeline,acmiyaguchi/data-pipeline,nathwill/data-pipeline