Hangs on v2.x HEAD if invalid MCA params specified

[jsquyres]

In testing both #2149 and the v2.x branch without that PR, I noticed that in some cases, if you specify a bogus MCA param on the mpirun command line, mpirun will hang. The orteds will be running on the target nodes (my tests were in an salloc allocation), but the MPI application was never launched.

For example:

$ mpirun --mca btl_bogus_flags send,put,get ring_c

Note the bogus MCA param name.

Sometimes this will hang (and not necessarily for all bogus MCA params, and/or if you add in a 2nd real MCA param on the command line, ...etc). Testing yields inconsistent results, suggesting some kind of memory error.

Some testing on master suggested that the problem may not be occurring over there (but if there's a real memory problem, my testing could have just gotten lucky / not triggered the same error by coincidence).

[jsquyres]

Nope! This was a red herring; the real issue will be filed in a new issue.