Just because the openib BTL can't reach a process doesn't mean it is a job-ending error. If we have other methods for reaching the process (e.g., sm for a local proc), then that's okay. If there is no method for reaching a proc, then that's an error - but the BML will report that situation.

The question of whether or not the openib BTL supports loopback is a separate question. It may be more appropriate to make the modex be PMIX_GLOBAL for cases where openib can support loopback so someone can run without a shared memory component. I'll leave that decision to the IB vendors.