[OMPI users] Improving error messages

[Scott Atchley]

Hi all,

We had a customer using 1.2.6 with MX. We were running his jobs, some  
of which used the MX BTL and some used the MX MTL.

He added a few more nodes to the cluster and installed the same OMPI.  
When we tried to run jobs that spanned the new nodes, the jobs failed.  
I did not keep the error messages, but it seems to be a standard  
message about a component such as "self" not found.

The problem in fact was that he installed OMPI, but for some reason  
neither the MX BTL nor the MX MTL were installed. Thus, the failure. I  
do not believe the error message for the BTL runs ever specifically  
mentioned a missing MX component even though we were setting "--mca  
btl self,sm,mx" (we did not specify MX when using the MTL, we only  
used "--mca pml cm".

It would be helpful in the case where a OMPI cannot run _and_ a module  
is specifically requested but not available to be mentioned in the  
error message.

Thanks,

Scott